Shape-conformable alkali metal battery having a conductive and deformable quasi-solid polymer electrode

ABSTRACT

Provided is an alkali metal cell comprising: (a) a quasi-solid cathode containing 30% to 95% by volume of a cathode active material, about 5% to about 40% by volume of a first electrolyte containing an alkali salt dissolved in a solvent and an ion-conducting polymer dissolved, dispersed in or impregnated by a solvent, and about 0.01% to about 30% by volume of a conductive additive wherein the conductive additive, containing conductive filaments, forms a 3D network of electron-conducting pathways such that the quasi-solid electrode has an electrical conductivity from about 10−6 S/cm to about 300 S/cm; (b) an anode; and (c) an ion-conducting membrane or porous separator disposed between the anode and the quasi-solid cathode; wherein the quasi-solid cathode has a thickness from 200 μm to 100 cm and a cathode active material having an active material mass loading greater than 10 mg/cm2.

FIELD OF THE INVENTION

The present invention relates generally to the field of alkali metalbatteries, including rechargeable lithium metal batteries, sodium metalbatteries, lithium-ion batteries, sodium-ion batteries, lithium-ioncapacitors and sodium-ion capacitors.

BACKGROUND OF THE INVENTION

Historically, today's most favorite rechargeable energy storagedevices—lithium-ion batteries—actually evolved from rechargeable“lithium metal batteries” using lithium (Li) metal or Li alloy as theanode and a Li intercalation compound as the cathode. Li metal is anideal anode material due to its light weight (the lightest metal), highelectronegativity (−3.04 V vs. the standard hydrogen electrode), andhigh theoretical capacity (3,860 mAh/g). Based on these outstandingproperties, lithium metal batteries were proposed 40 years ago as anideal system for high energy-density applications. During the mid-1980s,several prototypes of rechargeable Li metal batteries were developed. Anotable example was a battery composed of a Li metal anode and amolybdenum sulfide cathode, developed by MOLI Energy, Inc. (Canada).This and several other batteries from different manufacturers wereabandoned due to a series of safety problems caused by sharply uneven Ligrowth (formation of Li dendrites) as the metal was re-plated duringeach subsequent recharge cycle. As the number of cycles increases, thesedendritic or tree-like Li structures could eventually traverse theseparator to reach the cathode, causing internal short-circuiting.

To overcome these safety issues, several alternative approaches wereproposed in which either the electrolyte or the anode was modified. Oneapproach involved replacing Li metal by graphite (another Li insertionmaterial) as the anode. The operation of such a battery involvesshuttling Li ions between two Li insertion compounds, hence the name“Li-ion battery.” Presumably because of the presence of Li in its ionicrather than metallic state, Li-ion batteries are inherently safer thanLi-metal batteries.

Lithium ion battery is a prime candidate energy storage device forelectric vehicle (EV), renewable energy storage, and smart gridapplications. The past two decades have witnessed a continuousimprovement in Li-ion batteries in terms of energy density, ratecapability, and safety, and somehow the significantly higher energydensity Li metal batteries have been largely overlooked. However, theuse of graphite-based anodes in Li-ion batteries has several significantdrawbacks: low specific capacity (theoretical capacity of 372 mAh/g asopposed to 3,860 mAh/g for Li metal), long Li intercalation time (e.g.low solid-state diffusion coefficients of Li in and out of graphite andinorganic oxide particles) requiring long recharge times (e.g. 7 hoursfor electric vehicle batteries), inability to deliver high pulse power(power density<<1 kW/kg), and necessity to use pre-lithiated cathodes(e.g. lithium cobalt oxide), thereby limiting the choice of availablecathode materials. Further, these commonly used cathodes have arelatively low specific capacity (typically <200 mAh/g). These factorshave contributed to the two major shortcomings of today's Li-ionbatteries—low gravimetric and volumetric energy densities (typically150-220 Wh/kg and 450-600 Wh/L) and low power densities (typically <0.5kW/kg and <1.0 kW/L), all based on the total battery cell weight orvolume.

The emerging EV and renewable energy industries demand the availabilityof rechargeable batteries with a significantly higher gravimetric energydensity (e.g. demanding >>250 Wh/kg and, preferably, >>300 Wh/kg) andhigher power density (shorter recharge times) than what the current Liion battery technology can provide. Furthermore, the microelectronicsindustry is in need of a battery having a significantly largervolumetric energy density (>650 Wh/L, preferably >750 Wh/L) sinceconsumers demand to have smaller-volume and more compact portabledevices (e.g. smart phones and tablets) that store more energy. Theserequirements have triggered considerable research efforts on thedevelopment of electrode materials with a higher specific capacity,excellent rate capability, and good cycle stability for lithium ionbatteries.

Several elements from Group III, IV, and V in the periodic table canform alloys with Li at certain desired voltages. Therefore, variousanode materials based on such elements and some metal oxides have beenproposed for lithium ion batteries. Among these, silicon has beenrecognized as one of the next-generation anode materials for high-energylithium ion batteries since it has a nearly 10 times higher theoreticalgravimetric capacity than graphite 3,590 mAh/g based on Li_(3.75)Si vs.372 mAh/g for LiC₆) and ˜3 times larger volumetric capacities. However,the dramatic volume changes (up to 380%) of Si during lithium ionalloying and de-alloying (cell charge and discharge) often led to severeand rapid battery performance deterioration. The performance fade ismainly due to the volume change-induced pulverization of Si and theinability of the binder/conductive additive to maintain the electricalcontact between the pulverized Si particles and the current collector.In addition, the intrinsic low electric conductivity of silicon isanother challenge that needs to be addressed.

Although several high-capacity anode active materials have been found(e.g., Si), there has been no corresponding high-capacity cathodematerial available. Current cathode active materials commonly used inLi-ion batteries have the following serious drawbacks:

-   -   (1) The practical capacity achievable with current cathode        materials (e.g. lithium iron phosphate and lithium transition        metal oxides) has been limited to the range of 150-250 mAh/g        and, in most cases, less than 200 mAh/g.    -   (2) The insertion and extraction of lithium in and out of these        commonly used cathodes rely upon extremely slow solid-state        diffusion of Li in solid particles having very low diffusion        coefficients (typically 10⁻⁸ to 10⁻¹⁴ cm²/s), leading to a very        low power density (another long-standing problem of today's        lithium-ion batteries).    -   (3) The current cathode materials are electrically and thermally        insulating, not capable of effectively and efficiently        transporting electrons and heat. The low electrical conductivity        means high internal resistance and the necessity to add a large        amount of conductive additives, effectively reducing the        proportion of electrochemically active material in the cathode        that already has a low capacity. The low thermal conductivity        also implies a higher tendency to undergo thermal runaway, a        major safety issue in lithium battery industry.

Low-capacity anode or cathode active materials are not the only problemthat the lithium-ion battery industry faces. There are serious designand manufacturing issues that the lithium-ion battery industry does notseem to be aware of, or has largely ignored. For instance, despite thehigh gravimetric capacities at the electrode level (based on the anodeor cathode active material weight alone) as frequently claimed in openliterature and patent documents, these electrodes unfortunately fail toprovide batteries with high capacities at the battery cell or pack level(based on the total battery cell weight or pack weight). This is due tothe notion that, in these reports, the actual active material massloadings of the electrodes are too low. In most cases, the activematerial mass loadings of the anode (areal density) is significantlylower than 15 mg/cm² and mostly <8 mg/cm² (areal density=the amount ofactive materials per electrode cross-sectional area along the electrodethickness direction). The cathode active material amount is typically1.5-2.5 times higher than the anode active material. As a result, theweight proportion of the anode active material (e.g. graphite or carbon)in a lithium-ion battery is typically from 12% to 17%, and that of thecathode active material (e.g. LiMn₂O₄) from 17% to 35% (mostly <30%).The weight fraction of the cathode and anode active materials combinedis typically from 30% to 45% of the cell weight.

As a totally distinct class of energy storage device, sodium batterieshave been considered as an attractive alternative to lithium batteriessince sodium is abundant and the production of sodium is significantlymore environmentally benign compared to the production of lithium. Inaddition, the high cost of lithium is a major issue.

Sodium ion batteries using a hard carbon-based anode (Na-carbonintercalation compound) and a sodium transition metal phosphate as acathode have been described by several research groups. However, thesesodium-based devices exhibit even lower specific energies and ratecapabilities than Li-ion batteries. These conventional sodium-ionbatteries require sodium ions to diffuse in and out of a sodiumintercalation compound at both the anode and the cathode. The requiredsolid-state diffusion processes for sodium ions in a sodium-ion batteryare even slower than the Li diffusion processes in a Li-ion battery,leading to excessively low power densities.

Instead of hard carbon or other carbonaceous intercalation compound,sodium metal may be used as the anode active material in a sodium metalcell. However, the use of metallic sodium as the anode active materialis normally considered undesirable and dangerous because of dendriteformation, interface aging, and electrolyte incompatibility problems.Most significantly, the same flammable solvents previously used forlithium secondary batteries are also used in most of the sodium metal orsodium-ion batteries.

The low active material mass loading is primarily due to the inabilityto obtain thicker electrodes (thicker than 100-200 μm) using theconventional slurry coating procedure. This is not a trivial task as onemight think, and in reality the electrode thickness is not a designparameter that can be arbitrarily and freely varied for the purpose ofoptimizing the cell performance. Contrarily, thicker samples tend tobecome extremely brittle or of poor structural integrity and would alsorequire the use of large amounts of binder resin. The low arealdensities and low volume densities (related to thin electrodes and poorpacking density) result in a relatively low volumetric capacity and lowvolumetric energy density of the battery cells.

With the growing demand for more compact and portable energy storagesystems, there is keen interest to increase the utilization of thevolume of the batteries. Novel electrode materials and designs thatenable high volumetric capacities and high mass loadings are essentialto achieving improved cell volumetric capacities and energy densities.

With electronic devices becoming more compact and electric vehicles (EV)becoming of lighter weight, there is a pressing need for a high-energydensity battery that is shape-conformable so that it can be fitted intosome odd-shape or confined spaces in a device or vehicle. Byimplementing a battery in a space that otherwise would be an empty(unused or “wasted”) space (e.g. part of a car door or roof top), onecan make the device more compact or make the EV capable of storing morepower. In order to make the battery shape-conformable, the electrodesmust be deformable, flexible, and shape-conformable.

Therefore, there is clear and urgent need for lithium and sodiumbatteries that have high active material mass loading (high arealdensity), high electrode thickness or volume without compromisingconductivity, high-rate capability, high power density, and high energydensity. These batteries must be produced in an environmentally benignmanner. Further, the battery must be shape-conformable.

SUMMARY OF THE INVENTION

The present invention provides a method of producing a lithium batteryor sodium battery having a high active material mass loading,exceptionally low overhead weight and volume (relative to the activematerial mass and volume), high capacity, and unprecedentedly highenergy density and power density. This lithium or sodium battery can bea primary battery (non-rechargeable) or a secondary battery(rechargeable), including a rechargeable lithium or sodium metal battery(having a lithium or sodium metal anode) and a lithium-ion or sodium-ionbattery (e.g. having a first lithium intercalation compound as an anodeactive material and a second lithium intercalation or absorbingcompound, having a much higher electrochemical potential than the firstone, as a cathode active material). This alkali battery also includeslithium-ion capacitor and sodium-ion capacitor, wherein the anode is alithium-ion or sodium-ion cell type of anode and the cathode is asupercapacitor cathode (e.g. activated carbon or graphene sheets as anactive material for use in an electric double layer capacitor or a redoxpseudo-capacitor).

In certain embodiments, the invention provides an alkali metal cellcomprising: (a) a quasi-solid cathode containing about 30% to about 95%by volume of a cathode active material, about 5% to about 40% by volumeof a first electrolyte containing an alkali salt dissolved in a solventand an ion-conducting polymer dissolved in, dispersed in, or impregnatedby this solvent, and about 0.01% to about 30% by volume of a conductiveadditive wherein the conductive additive, containing conductivefilaments, forms a 3D network of electron-conducting pathways such thatthe quasi-solid electrode has an electrical conductivity from about 10⁻⁶S/cm to about 300 S/cm; (b) an anode; and (c) an ion-conducting membraneor porous separator disposed between the anode and the quasi-solidcathode; wherein said quasi-solid cathode has a thickness no less than200 μm. The quasi-solid cathode preferably contains a cathode activematerial mass loading no less than 10 mg/cm², preferably no less than 15mg/cm², further preferably no less than 25 mg/cm², more preferably noless than 35 mg/cm², still more preferably no less than 45 mg/cm², andmost preferably greater than 65 mg/cm².

In this cell, the anode may contain a quasi-solid anode containing about30% to about 95% by volume of an anode active material, about 5% toabout 40% by volume of a second electrolyte containing an alkali saltdissolved in a solvent and an ion-conducting polymer dissolved in,dispersed in, or impregnated by this solvent, and about 0.01% to about30% by volume of a conductive additive wherein said conductive additive,containing conductive filaments, forms a 3D network ofelectron-conducting pathways such that the quasi-solid electrode has anelectrical conductivity from about 10⁻⁶ S/cm to about 300 S/cm; whereinsaid quasi-solid anode has a thickness no less than 200 μm. Thequasi-solid anode preferably contains an anode active material massloading no less than 10 mg/cm², preferably no less than 15 mg/cm²,further preferably no less than 25 mg/cm², more preferably no less than35 mg/cm², still more preferably no less than 45 mg/cm², and mostpreferably greater than 65 mg/cm². The first electrolyte may be the sameas or different from the second electrolyte in composition andstructure.

In certain embodiments, the invention provides an alkali metal cellcomprising: (A) a quasi-solid anode containing about 30% to about 95% byvolume of an anode active material, about 5% to about 40% by volume ofan electrolyte containing an alkali salt dissolved in a solvent anion-conducting polymer dissolved in, dispersed in, or impregnated bythis solvent, and about 0.01% to about 30% by volume of a conductiveadditive wherein the conductive additive, containing conductivefilaments, forms a 3D network of electron-conducting pathways such thatthe quasi-solid electrode has an electrical conductivity from about 10⁻⁶S/cm to about 300 S/cm; (B) a cathode; and (C) an ion-conductingmembrane or porous separator disposed between the quasi-solid anode andthe cathode. Preferably, the quasi-solid cathode has a thickness no lessthan 200 μm.

The presently invented quasi-solid polymer electrodes are deformable,flexible, and shape-conformable, enabling a shape-conformable battery.

The present invention also provides a method of preparing an alkalimetal cell having a quasi-solid electrode, the method comprising: (a)combining a quantity of an active material (an anode active material ora cathode active material), a quantity of an electrolyte containing analkali salt dissolved in a solvent an ion-conducting polymer dissolvedin, dispersed in, or impregnated by this solvent, and a conductiveadditive to form a deformable and electrically conductive electrodematerial, wherein the conductive additive, containing conductivefilaments, forms a 3D network of electron-conducting pathways; (b)forming the electrode material into a quasi-solid electrode, wherein theforming step includes deforming the electrode material into an electrodeshape without interrupting the 3D network of electron-conductingpathways such that the electrode maintains an electrical conductivity noless than 10⁻⁶ S/cm (preferably no less than 10⁻⁵ S/cm, more preferablyno less than 10⁻³ S/cm, further preferably no less than 10⁻² S/cm, stillmore preferably and typically no less than 10⁻¹ S/cm, even moretypically and preferably no less than 1 S/cm, and further more typicallyand preferably no less than 10 S/cm and up to 300 S/cm); (c) forming asecond electrode (the second electrode may be a quasi-solid electrode aswell); and (d) forming an alkali metal cell by combining the quasi-solidelectrode and the second electrode having an ion-conducting separatordisposed between the two electrodes.

In some embodiments, the electrolyte (including the first electrolyte orthe second electrolyte) contains a lithium ion-conducting or sodiumion-conducting polymer selected from poly(ethylene oxide) (PEO, having amolecular weight lower than 1×10⁶ g/mole), polypropylene oxide (PPO),poly(acrylonitrile) (PAN), poly(methyl methacrylate) (PMMA),poly(vinylidene fluoride) (PVdF), poly bis-methoxyethoxyethoxide-phosphazenex, polyvinyl chloride, Polydimethylsiloxane,poly(vinylidene fluoride)-hexafluoropropylene (PVDF-HFP), a sulfonatedderivative thereof, a sulfonated polymer, or a combination thereof.Sulfonation is herein found to impart improved lithium ion conductivityto a polymer. A PEO molecular weight higher than 1×10⁶ g/mole typicallymakes PEO insoluble and non-dispersible in a solvent.

Typically and preferably, this ion-conducting polymer does not form amatrix (continuous phase) in the electrode.

The ion-conducting polymer may be selected from the group consisting ofpoly(perfluoro sulfonic acid), sulfonated polytetrafluoroethylene,sulfonated perfluoroalkoxy derivatives of polytetrafluoroethylene,sulfonated polysulfone, sulfonated poly(ether ketone), sulfonated poly(ether ether ketone), sulfonated polystyrene, sulfonated polyimide,sulfonated styrene-butadiene copolymers, sulfonated polychloro-trifluoroethylene (PCTFE), sulfonated perfluoroethylene-propylenecopolymer (FEP), sulfonated ethylene-chlorotrifluoroethylene copolymer(ECTFE), sulfonated polyvinylidenefluoride (PVDF), sulfonated copolymersof polyvinylidenefluoride with hexafluoropropene andtetrafluoroethylene, sulfonated copolymers of ethylene andtetrafluoroethylene (ETFE), sulfonated polybenzimidazole (PBI), theirchemical derivatives, copolymers, blends and combinations thereof. Wehave surprisingly observed that these sulfonated polymers are bothlithium ion-conducting and sodium ion-conducting.

A “filament” is a solid material object having a largest dimension (e.g.length) and a smallest dimension (e.g. diameter or thickness) and thelargest dimension-to-smallest dimension ratio is greater than 3,preferably greater than 10, and further preferably greater than 100.Typically, this is a wire-like, fiber-like, needle-like, rod-like,platelet-like, sheet-like, ribbon-like, or disc-like object, just toname a few. In certain embodiments, the conductive filaments areselected from carbon fibers, graphite fibers, carbon nano-fibers,graphite nano-fibers, carbon nanotubes, needle coke, carbon whiskers,conductive polymer fibers, conductive material-coated fibers, metalnano-wires, metal fibers, metal wires, graphene sheets, expandedgraphite platelets, a combination thereof, or a combination thereof withnon-filamentary conductive particles.

In certain embodiments, the electrode maintains an electricalconductivity from 10⁻⁵ S/cm to about 1 S/cm.

In certain embodiments, the deformable electrode material has anapparent viscosity of no less than about 10,000 Pa-s measured at anapparent shear rate of 1,000 s⁻¹. In certain embodiments, the deformableelectrode material has an apparent viscosity of no less than about100,000 Pa-s at an apparent shear rate of 1,000 s⁻¹.

In the method, the quantity of the active material is typically fromabout 20% to about 95% by volume of the electrode material, moretypically from about 35% to about 85% by volume of the electrodematerial, and most typically from about 50% to about 75% by volume ofthe electrode material.

Preferably, the step of combining active material, conductive additive,and electrolyte (including dissolving a lithium or sodium salt in aliquid solvent) follows a specific sequence. This step includes firstdispersing the conductive filaments into a liquid solvent to form ahomogeneous suspension, followed by adding the active material in thesuspension and by dissolving a lithium salt or sodium salt in the liquidsolvent and by dissolving or dispersing the ion-conducting polymer inthe solvent. In other words, the conductive filaments must be uniformlydispersed in the liquid solvent first prior to adding other ingredients,such as active material and the ion-conducting polymer, and prior todissolving the lithium salt or sodium salt in the solvent. This sequenceis essential to achieving percolation of conducting filaments forforming a 3D network of electron-conducting pathways at a lowerconductive filament volume fraction (lower threshold volume fraction).Without following such a sequence, the percolation of conductingfilaments may not occur or occur only when an excessively largeproportion of conducting filaments (e.g. >10% by volume) is added, whichwould reduce the fraction of active material and thus reduce the energydensity of the cell.

In certain embodiments, the steps of combining and forming the electrodematerial into a quasi-solid electrode include dissolving a lithium salt(or sodium salt) and an ion-conducting polymer in a liquid solvent toform a polymer electrolyte having a first salt concentration and firstpolymer concentration and subsequently removing portion of the liquidsolvent to increase the salt concentration to obtain a quasi-solidpolymer electrolyte having a second salt concentration and secondpolymer concentration, which are higher than the first concentrationsand preferably higher than 2.5 M of combined salt and polymer (and morepreferably from 3.0 M to 14 M).

The step of removing portion of solvent may be conducted in such amanner that it does not cause precipitation or crystallization of thesalt and polymer and that the electrolyte is in a supersaturated state.In certain preferred embodiments, the liquid solvent contains a mixtureof at least a first liquid solvent and a second liquid solvent and thefirst liquid solvent is more volatile than the second liquid solvent,wherein the step of removing portion of the liquid solvent includespartially or fully removing the first liquid solvent.

There is no restriction on the types of anode active materials orcathode active materials that can be used in practicing the instantinvention. However, preferably, the anode active material absorbslithium ions at an electrochemical potential of less than 1.0 volt(preferably less than 0.7 volts) above the Li/Li⁺ (i.e. relative toLi→Li⁺+e⁻ as the standard potential) when the battery is charged.

In certain preferred embodiments, the alkali metal cell is a lithiummetal battery, lithium-ion battery, or lithium-ion capacitor, whereinthe anode active material is selected from the group consisting of: (a)Particles of lithium metal or a lithium metal alloy; (b) Naturalgraphite particles, artificial graphite particles, meso-carbonmicrobeads (MCMB), carbon particles (including soft carbon and hardcarbon), needle coke, carbon nanotubes, carbon nano-fibers, carbonfibers, and graphite fibers; (c) silicon (Si), germanium (Ge), tin (Sn),lead (Pb), antimony (Sb), bismuth (Bi), zinc (Zn), aluminum (Al), nickel(Ni), cobalt (Co), manganese (Mn), titanium (Ti), iron (Fe), and cadmium(Cd); (d) Alloys or intermetallic compounds of Si, Ge, Sn, Pb, Sb, Bi,Zn, Al, or Cd with other elements, wherein said alloys or compounds arestoichiometric or non-stoichiometric; (e) Oxides, carbides, nitrides,sulfides, phosphides, selenides, and tellurides of Si, Ge, Sn, Pb, Sb,Bi, Zn, Al, Fe, Ni, Co, Ti, Mn, or Cd, and their mixtures or composites;(f) Pre-lithiated versions thereof; (g) Pre-lithiated graphene sheets;and combinations thereof.

In certain embodiments, the alkali metal cell is a sodium metal cell orsodium-ion cell and the active material is an anode active materialcontaining a sodium intercalation compound selected from petroleum coke,amorphous carbon, activated carbon, hard carbon (carbon that isdifficult to graphitize), soft carbon (carbon that can be readilygraphitized), templated carbon, hollow carbon nanowires, hollow carbonsphere, titanates, NaTi₂(PO₄)₃, Na₂Ti₃O₇, Na₂C₈H₄O₄, Na₂TP, Na_(x)TiO₂(x=0.2 to 1.0), Na₂C₈H₄O₄, carboxylate based materials, C₈H₄Na₂O₄,C₈H₆O₄, C₈H₅NaO₄, C₈Na₂F₄O₄, C₁₀H₂Na₄O₈, C₁₄H₄O₆, C₁₄H₄Na₄O₈, or acombination thereof.

In certain embodiments, the alkali metal cell is a sodium metal cell orsodium-ion cell and the active material is an anode active materialselected from the group consisting of: (a) Particles of sodium metal ora sodium metal alloy; (b) Natural graphite particles, artificialgraphite particles, meso-carbon microbeads (MCMB), carbon particles,needle coke, carbon nanotubes, carbon nano-fibers, carbon fibers, andgraphite fibers; (c) Sodium-doped silicon (Si), germanium (Ge), tin(Sn), lead (Pb), antimony (Sb), bismuth (Bi), zinc (Zn), aluminum (Al),titanium (Ti), cobalt (Co), nickel (Ni), manganese (Mn), cadmium (Cd),and mixtures thereof; (d) Sodium-containing alloys or intermetalliccompounds of Si, Ge, Sn, Pb, Sb, Bi, Zn, Al, Ti, Co, Ni, Mn, Cd, andtheir mixtures; (e) Sodium-containing oxides, carbides, nitrides,sulfides, phosphides, selenides, tellurides, or antimonides of Si, Ge,Sn, Pb, Sb, Bi, Zn, Al, Fe, Ti, Co, Ni, Mn, Cd, and mixtures orcomposites thereof; (f) Sodium salts; and (g) Graphene sheets pre-loadedwith sodium ions; and combinations thereof.

In certain embodiments, the alkali metal cell is a sodium metal cell orsodium-ion cell and the active material is a cathode active materialcontaining a sodium intercalation compound or sodium-absorbing compoundselected from an inorganic material, an organic or polymeric material, ametal oxide/phosphate/sulfide, or a combination thereof. The metaloxide/phosphate/sulfide may be selected from a sodium cobalt oxide,sodium nickel oxide, sodium manganese oxide, sodium vanadium oxide,sodium-mixed metal oxide, sodium/potassium-transition metal oxide,sodium iron phosphate, sodium/potassium iron phosphate, sodium manganesephosphate, sodium/potassium manganese phosphate, sodium vanadiumphosphate, sodium/potassium vanadium phosphate, sodium mixed metalphosphate, transition metal sulfide, or a combination thereof.

The inorganic material may be selected from sulfur, sulfur compound,lithium polysulfide, transition metal dichalcogenide, a transition metaltrichalcogenide, or a combination thereof. In certain embodiments, theinorganic material is selected from TiS₂, TaS₂, MoS₂, NbSe₃, MnO₂, CoO₂,an iron oxide, a vanadium oxide, or a combination thereof.

In some embodiments, the alkali metal cell is a sodium metal cell orsodium-ion cell and the active material is a cathode active materialcontaining a sodium intercalation compound selected from NaFePO₄,Na_((1-x))K_(x)PO₄, Na_(0.7)FePO₄, Na_(1.5)VOPO₄F_(0.5), Na₃V₂(PO₄)₃,Na₃V₂(PO₄)₂F₃, Na₂FePO₄F, NaFeF₃, NaVPO₄F, Na₃V₂(PO₄)₂F₃,Na_(1.5)VOPO₄F_(0.5), Na₃V₂(PO₄)₃, NaV₆O₁₅, Na_(x)VO₂, Na_(0.33)V₂O₅,Na_(x)CoO₂, Na_(2/3)[Ni_(1/3)Mn_(2/3)]O₂, Na_(x)(Fe_(1/2)Mn_(1/2))O₂,Na_(x)MnO₂, λ-MnO₂, Na_(x)K_((1-x))MnO₂, Na_(0.44)MnO₂, Na_(0.44)MnO₂/C,Na₄Mn₉O₁₈, NaFe₂Mn(PO₄)₃, Na₂Ti₃O₇, Ni_(1/3)Mn_(1/3)Co_(1/3)O₂,Cu_(0.56)Ni_(0.44)HCF, NiHCF, Na_(x)MnO₂, NaCrO₂, Na₃Ti₂(PO₄)₃, NiCo₂O₄,Ni₃S₂/FeS₂, Sb₂O₄, Na₄Fe(CN)₆/C, NaV_(1-x)Cr_(x)PO₄F, Se_(z)S_(y)(y/z=0.01 to 100), Se, Alluaudites, or a combination thereof, wherein xis from 0.1 to 1.0.

In some preferred embodiments, the cathode active material contains alithium intercalation compound selected from the group consisting oflithium cobalt oxide, doped lithium cobalt oxide, lithium nickel oxide,doped lithium nickel oxide, lithium manganese oxide, doped lithiummanganese oxide, lithium vanadium oxide, doped lithium vanadium oxide,lithium mixed-metal oxides, lithium iron phosphate, lithium vanadiumphosphate, lithium manganese phosphate, lithium mixed-metal phosphates,metal sulfides, and combinations thereof.

The electrolytes can contain water, organic liquid, ionic liquid (ionicsalt having a melting temperature lower than 100° C., preferably lowerthan room temperature, 25° C.), or a mixture of an ionic liquid and anorganic liquid at a ratio from 1/100 to 100/1. The organic liquid isdesirable, but the ionic liquid is preferred. The electrolyte typicallyand preferably contains a high solute concentration (concentration oflithium/sodium salt and polymer combined) that brings the solute to asaturated or supersaturated state in the resulting electrode (anode orcathode). Such an electrolyte is essentially a polymer electrolyte thatbehaves like a deformable or conformable solid. This is fundamentallydistinct from a liquid electrolyte or polymer gel electrolyte.

In a preferred embodiment, the quasi-solid electrode has a thicknessfrom 200 μm to 1 cm, preferably from 300 μm to 0.5 cm (5 mm), furtherpreferably from 400 μm to 3 mm, and most preferably from 500 μm to 2.5mm (2,500 μm). If the active material is an anode active material, theanode active material has a mass loading no less than 25 mg/cm²(preferably no less than 30 mg/cm², and more preferably no less than 35mg/cm²) and/or occupies at least 25% (preferably at least 30% and morepreferably at least 35%) by weight or by volume of the entire batterycell. If the active material is a cathode active material, the cathodeactive material preferably has a mass loading no less than 20 mg/cm²(preferably no less than 25 mg/cm² and more preferably no less than 30mg/cm²) for an organic or polymer material or no less than 45 mg/cm²(preferably no less than 50 mg/cm² and more preferably no less than 55mg/cm²) for an inorganic and non-polymer material in the cathode and/oroccupies at least 45% (preferably at least 50% and more preferably atleast 55%) by weight or by volume of the entire battery cell.

The aforementioned requirements on electrode thickness, the anode activematerial areal mass loading or mass fraction relative to the entirebattery cell, or the cathode active material areal mass loading or massfraction relative to the entire battery cell have not been possible withconventional lithium or sodium batteries using the conventional slurrycoating and drying process.

In some embodiments, the anode active material is a pre-lithiatedversion of graphene sheets selected from pristine graphene, grapheneoxide, reduced graphene oxide, graphene fluoride, graphene chloride,graphene bromide, graphene iodide, hydrogenated graphene, nitrogenatedgraphene, boron-doped graphene, nitrogen-doped graphene, chemicallyfunctionalized graphene, a physically or chemically activated or etchedversion thereof, or a combination thereof. Surprisingly, withoutpre-lithiation, the resulting lithium battery cell does not exhibit asatisfactory cycle life (i.e. capacity decays rapidly).

In some embodiments of the invented method, the cell is a lithium metalcell or lithium-ion cell containing a cathode active material selectedfrom a lithium intercalation compound or lithium-absorbing compound isselected from an inorganic material, an organic or polymeric material, ametal oxide/phosphate/sulfide, or a combination thereof. For example,the metal oxide/phosphate/sulfide may be selected from a lithium cobaltoxide, lithium nickel oxide, lithium manganese oxide, lithium vanadiumoxide, lithium-mixed metal oxide, lithium iron phosphate, lithiummanganese phosphate, lithium vanadium phosphate, lithium mixed metalphosphate, transition metal sulfide, or a combination thereof. Theinorganic material is selected from sulfur, sulfur compound, lithiumpolysulfide, transition metal dichalcogenide, a transition metaltrichalcogenide, or a combination thereof. In particular, the inorganicmaterial is selected from TiS₂, TaS₂, MoS₂, NbSe₃, MnO₂, CoO₂, an ironoxide, a vanadium oxide, or a combination thereof. These will be furtherdiscussed later.

In this lithium metal battery, the cathode active material contains alithium intercalation compound selected from a metal carbide, metalnitride, metal boride, metal dichalcogenide, or a combination thereof.In some embodiments, the cathode active material contains a lithiumintercalation compound selected from an oxide, dichalcogenide,trichalcogenide, sulfide, selenide, or telluride of niobium, zirconium,molybdenum, hafnium, tantalum, tungsten, titanium, vanadium, chromium,cobalt, manganese, iron, or nickel in a nanowire, nano-disc,nano-ribbon, or nano platelet form. Preferably, the cathode activematerial contains a lithium intercalation compound selected fromnanodiscs, nanoplatelets, nano-coating, or nanosheets of an inorganicmaterial selected from: (a) bismuth selenide or bismuth telluride, (b)transition metal dichalcogenide or trichalcogenide, (c) sulfide,selenide, or telluride of niobium, zirconium, molybdenum, hafnium,tantalum, tungsten, titanium, cobalt, manganese, iron, nickel, or atransition metal; (d) boron nitride, or (e) a combination thereof;wherein said discs, platelets, or sheets have a thickness less than 100nm.

In some embodiments, the cathode active material in this lithium metalbattery is an organic material or polymeric material selected fromPoly(anthraquinonyl sulfide) (PAQS), a lithium oxocarbon,3,4,9,10-perylenetetracarboxylic dianhydride (PTCDA),poly(anthraquinonyl sulfide), pyrene-4,5,9,10-tetraone (PYT),polymer-bound PYT, Quino(triazene), redox-active organic material,Tetracyanoquinodimethane (TCNQ), tetracyanoethylene (TCNE),2,3,6,7,10,11-hexamethoxytriphenylene (HMTP), poly(5-amino-1,4-dyhydroxyanthraquinone) (PADAQ), phosphazene disulfide polymer ([(NPS₂)₃]n),lithiated 1,4,5,8-naphthalenetetraol formaldehyde polymer,Hexaazatrinaphtylene (HATN), Hexaazatriphenylene hexacarbonitrile(HAT(CN)₆), 5-Benzylidene hydantoin, Isatine lithium salt, Pyromelliticdiimide lithium salt, tetrahydroxy-p-benzoquinone derivatives (THQLi₄),N,N′-diphenyl-2,3,5,6-tetraketopiperazine (PHP),N,N′-diallyl-2,3,5,6-tetraketopiperazine (AP),N,N′-dipropyl-2,3,5,6-tetraketopiperazine (PRP), a thioether polymer, aquinone compound, 1,4-benzoquinone, 5,7,12,14-pentacenetetrone (PT),5-amino-2,3-dihydro-1,4-dyhydroxy anthraquinone (ADDAQ),5-amino-1,4-dyhydroxy anthraquinone (ADAQ), calixquinone, Li₄C₆O₆,Li₂C₆O₆, Li₆C₆O₆, or a combination thereof.

The thioether polymer is selected fromPoly[methanetetryl-tetra(thiomethylene)] (PMTTM),Poly(2,4-dithiopentanylene) (PDTP), a polymer containingPoly(ethene-1,1,2,2-tetrathiol) (PETT) as a main-chain thioetherpolymers, a side-chain thioether polymer having a main-chain consistingof conjugating aromatic moieties, and having a thioether side chain as apendant, Poly(2-phenyl-1,3-dithiolane) (PPDT),Poly(1,4-di(1,3-dithiolan-2-yl)benzene)(PDDTB),poly(tetrahydrobenzodithiophene) (PTHBDT), poly[1,2,4,5-tetrakis(propylthio) benzene] (PTKPTB, or poly[3,4(ethylenedithio)thiophene](PEDTT).

In a preferred embodiment, the cathode active material is an organicmaterial containing a phthalocyanine compound selected from copperphthalocyanine, zinc phthalocyanine, tin phthalocyanine, ironphthalocyanine, lead phthalocyanine, nickel phthalocyanine, vanadylphthalocyanine, fluorochromium phthalocyanine, magnesium phthalocyanine,manganous phthalocyanine, dilithium phthalocyanine, aluminumphthalocyanine chloride, cadmium phthalocyanine, chlorogalliumphthalocyanine, cobalt phthalocyanine, silver phthalocyanine, ametal-free phthalocyanine, a chemical derivative thereof, or acombination thereof.

In the lithium metal battery, the cathode active material constitutes anelectrode active material loading greater than 30 mg/cm² (preferablygreater than 40 mg/cm², more preferably greater than 45 mg/cm², and mostpreferably greater than 50 mg/cm²) and/or wherein the electrode has athickness no less than 300 μm (preferably no less than 400 μm, morepreferably no less than 500 μm, can be up to or greater than 100 cm).There is no theoretical limit on the electrode thickness of thepresently invented alkali metal battery.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1(A) Schematic of a prior art lithium-ion battery cell composed ofan anode current collector, one or two anode active material layers(e.g. thin Si coating layers) coated on the two primary surfaces of theanode current collector, a porous separator and electrolyte, one or twocathode electrode layers (e.g. sulfur layers), and a cathode currentcollector;

FIG. 1(B) Schematic of a prior art lithium-ion battery, wherein theelectrode layer is composed of discrete particles of an active material(e.g. graphite or tin oxide particles in the anode layer or LiCoO₂ inthe cathode layer), conductive additives (not shown), and resin binder(not shown).

FIG. 1(C) Schematic of a presently invented lithium-ion battery cell,comprising a quasi-solid anode (consisting of anode active materialparticles and conductive filaments directly mixed or dispersed in anelectrolyte), a porous separator, and a quasi-solid cathode (consistingof cathode active material particles and conductive filaments directlymixed or dispersed in an electrolyte). In this embodiment, no resinbinder is required.

FIG. 1(D) Schematic of a presently invented lithium metal battery cell,comprising an anode (containing a lithium metal layer deposited on a Cufoil surface), a porous separator, and a quasi-solid cathode (consistingof cathode active material particles and conductive filaments directlymixed or dispersed in an electrolyte). In this embodiment, no resinbinder is required.

FIG. 2(A) Schematic of the closely packed, highly ordered structure of asolid electrolyte;

FIG. 2(B) Schematic of a totally amorphous liquid electrolyte havinglarge fractions of free volume through which cations (e.g. Na⁺) caneasily migrate;

FIG. 2(C) Schematic of the randomized or amorphous structure of aquasi-solid electrolyte having solvent molecules separating salt speciesto produce amorphous zones for easy migration of free (un-clustered)cations. The ion-conducting polymer is also brought into asupersaturated state that remains substantially amorphous.

FIG. 3(A) The Na⁺ ion transference numbers of electrolytes (e.g.(PEO+NaTFSI salt) in (DOL+DME) solvents) in relation to the sodium saltmolecular ratio x.

FIG. 3(B) The Na⁺ ion transference numbers of electrolytes (e.g.(PPO+NaTFSI salt) in (EMImTFSI+DOL) solvents) in relation to the sodiumsalt molecular ratio x.

FIG. 4 Schematic of a commonly used process for producing exfoliatedgraphite, expanded graphite flakes (thickness >100 nm), and graphenesheets (thickness <100 nm, more typically <10 nm, and can be as thin as0.34 nm).

FIG. 5(A) The electrical conductivity (percolation behavior) ofconducting filaments in a quasi-solid polymer electrode, plotted as afunction of the volume fraction of conductive filaments (carbonnano-fibers).

FIG. 5(B) The electrical conductivity (percolation behavior) ofconducting filaments in a quasi-solid polymer electrode, plotted as afunction of the volume fraction of conductive filaments (reducedgraphene oxide sheets).

FIG. 6 Ragone plots (gravimetric power density vs. energy density) oflithium-ion battery cells containing graphite particles as the anodeactive material and carbon-coated LFP particles as the cathode activematerials. Three of the 4 data curves are for the cells preparedaccording to an embodiment of instant invention and the remaining one bythe conventional slurry coating of electrodes (roll-coating).

FIG. 7 Ragone plots (gravimetric power density vs. gravimetric energydensity) of three cells, each containing graphene-embraced Si nanoparticles as the anode active material and LiCoO₂ nano particles as thecathode active material. The experimental data were obtained from theLi-ion battery cells that were prepared by the presently invented method(following sequences S1 and S3) and that by the conventional slurrycoating of electrodes.

FIG. 8 Ragone plots of lithium metal batteries containing a lithium foilas the anode active material, dilithium rhodizonate (Li₂C₆O₆) as thecathode active material, and lithium salt (LiPF₆)/PPO-PC/DEC as organicelectrolyte. The data are the lithium metal cells prepared by thepresently invented method (sequences S2 and S3 with 2 different saltconcentrations) and that by the conventional slurry coating ofelectrodes.

FIG. 9 Ragone plots of two sodium-ion capacitors each containingpre-sodiated hard carbon particles as the anode active material andgraphene sheets as the cathode active material; one cell having an anodeprepared by conventional slurry coating process and the other cellhaving a quasi-solid anode prepared according to a presently inventedmethod.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

This invention is directed at a lithium battery or sodium batteryexhibiting an exceptionally high volumetric energy density that hasnever been previously achieved. This battery can be a primary battery,but is preferably a secondary battery selected from a lithium-ionbattery, a lithium metal secondary battery (e.g. using lithium metal asan anode active material), a sodium-ion battery, a sodium metal battery,a lithium-ion capacitor, or a sodium-ion capacitor. The battery is basedon a quasi-solid polymer electrolyte, which contains a polymer and alithium or sodium salt dissolved in water, an organic solvent, an ionicliquid, or a mixture of organic and ionic liquid. Preferably theelectrolyte is a “quasi-solid polymer electrolyte” containing a highconcentration of solutes (a lithium salt or sodium salt and a polymer)in a solvent to the extent that it behaves like a solid, but remainsdeformable even when desirable amounts of conductive filaments and anactive material are added into the electrolyte (hence, the term“deformable quasi-solid polymer electrode”). The electrolyte is not aliquid electrolyte, nor a solid electrolyte. The shape of a lithiumbattery can be cylindrical, square, button-like, etc. The presentinvention is not limited to any battery shape or configuration.

For convenience, we will use selected materials, such as lithium ironphosphate (LFP), vanadium oxide (V_(x)O_(y)), dilithium rhodizonate(Li₂C₆O₆), and copper phthalocyanine (CuPc) as illustrative examples ofthe cathode active material, and graphite, hard carbon, SnO, Co₃O₄, andSi particles as examples of the anode active material. These should notbe construed as limiting the scope of the invention.

As illustrated in FIG. 1(A), a prior art lithium or sodium battery cellis typically composed of an anode current collector (e.g. Cu foil), ananode electrode or anode active material layer (e.g. Li metal foil,sodium foil, or prelithiated Si coating deposited on one or two sides ofa Cu foil), a porous separator and/or an electrolyte component, acathode electrode or cathode active material layer (or two cathodeactive material layers coated on two sides of an Al foil), and a cathodecurrent collector (e.g. Al foil).

In a more commonly used prior art cell configuration (FIG. 1(B)), theanode layer is composed of particles of an anode active material (e.g.graphite, hard carbon, or Si), a conductive additive (e.g. carbon blackparticles), and a resin binder (e.g. SBR or PVDF). The cathode layer iscomposed of particles of a cathode active material (e.g. LFP particles),a conductive additive (e.g. carbon black particles), and a resin binder(e.g. PVDF). Both the anode and the cathode layers are typically up to100-200 μm thick to give rise to a presumably sufficient amount ofcurrent per unit electrode area. This thickness range is considered anindustry-accepted constraint under which a battery designer normallyworks under. This thickness constraint is due to several reasons: (a)the existing battery electrode coating machines are not equipped to coatexcessively thin or excessively thick electrode layers; (b) a thinnerlayer is preferred based on the consideration of reduced lithium iondiffusion path lengths; but, too thin a layer (e.g. <100 μm) does notcontain a sufficient amount of an active lithium storage material(hence, insufficient current output); (c) thicker electrodes are proneto delaminate or crack upon drying or handling after roll-coating; and(d) all non-active material layers in a battery cell (e.g. currentcollectors and separator) must be kept to a minimum in order to obtain aminimum overhead weight and a maximum lithium storage capability and,hence, a maximized energy density (Wk/kg or Wh/L of cell).

In a less commonly used cell configuration, as illustrated in FIG. 1(A),either the anode active material (e.g. Si coating) or the cathode activematerial (e.g. lithium transition metal oxide) is deposited in a thinfilm form directly onto a current collector, such as a sheet of copperfoil or Al foil. However, such a thin film structure with an extremelysmall thickness-direction dimension (typically much smaller than 500 nm,often necessarily thinner than 100 nm) implies that only a small amountof active material can be incorporated in an electrode (given the sameelectrode or current collector surface area), providing a low totallithium storage capacity and low lithium storage capacity per unitelectrode surface area. Such a thin film must have a thickness less than100 nm to be more resistant to cycling-induced cracking (for the anode)or to facilitate a full utilization of the cathode active material. Sucha constraint further diminishes the total lithium storage capacity andthe lithium storage capacity per unit electrode surface area. Such athin-film battery has very limited scope of application.

On the anode side, a Si layer thicker than 100 nm has been found toexhibit poor cracking resistance during battery charge/discharge cycles.It takes but a few cycles for the Si layer to get fragmented. On thecathode side, a sputtered layer of lithium metal oxide thicker than 100nm does not allow lithium ions to fully penetrate and reach full body ofthe cathode layer, resulting in a poor cathode active materialutilization rate. A desirable electrode thickness is at least 100 μm,with individual active material coating or particle having a dimensiondesirably less than 100 nm. Thus, these thin-film electrodes (with athickness <100 nm) directly deposited on a current collector fall shortof the required thickness by three (3) orders of magnitude. As a furtherproblem, all of the cathode active materials are not conductive to bothelectrons and lithium ions. A large layer thickness implies anexcessively high internal resistance and a poor active materialutilization rate. Sodium batteries have similar issues.

In other words, there are several conflicting factors that must beconsidered concurrently when it comes to the design and selection of acathode or anode active material in terms of material type, size,electrode layer thickness, and active material mass loading. Thus far,there has been no effective solution offered by any prior art teachingto these often conflicting problems. We have solved these challengingissues, which have troubled battery designers and electrochemists alikefor more than 30 years, by developing a new method of producing lithiumbatteries or sodium batteries as herein disclosed.

The prior art lithium battery cell is typically made by a process thatincludes the following steps: (a) The first step is mixing particles ofthe anode active material (e.g. Si nano particles or meso-carbonmicro-beads, MCMBs), a conductive filler (e.g. graphite flakes), a resinbinder (e.g. PVDF) in a solvent (e.g. NMP) to form an anode slurry. On aseparate basis, particles of the cathode active material (e.g. LFPparticles), a conductive filler (e.g. acetylene black), a resin binder(e.g. PVDF) are mixed and dispersed in a solvent (e.g. NMP) to form acathode slurry. (b) The second step includes coating the anode slurryonto one or both primary surfaces of an anode current collector (e.g. Cufoil), drying the coated layer by vaporizing the solvent (e.g. NMP) toform a dried anode electrode coated on Cu foil. Similarly, the cathodeslurry is coated and dried to form a dried cathode electrode coated onAl foil. Slurry coating is normally done in a roll-to-roll manner in areal manufacturing situation; (c) The third step includes laminating ananode/Cu foil sheet, a porous separator layer, and a cathode/Al foilsheet together to form a 3-layer or 5-layer assembly, which is cut andslit into desired sizes and stacked to form a rectangular structure (asan example of shape) or rolled into a cylindrical cell structure. (d)The rectangular or cylindrical laminated structure is then encased in analuminum-plastic laminated envelope or steel casing. (e) A liquidelectrolyte is then injected into the laminated structure to make alithium battery cell.

There are several serious problems associated with the process and theresulting lithium battery cell:

-   -   1) It is very difficult to produce an electrode layer (anode        layer or cathode layer) that is thicker than 200 μm. There are        several reasons why this is the case. An electrode of 100-200 μm        thickness typically requires a heating zone of 30-50 meters long        in a slurry coating facility, which is too time consuming, too        energy intensive, and not cost-effective. For some electrode        active materials, such as metal oxide particles, it has not been        possible to produce an electrode of good structural integrity        that is thicker than 100 μm in a real manufacturing environment        on a continuous basis. The resulting electrodes are very fragile        and brittle. Thicker electrodes have a high tendency to        delaminate and crack.    -   2) With a conventional process, as depicted in FIG. 1(A), the        actual mass loadings of the electrodes and the apparent        densities for the active materials are too low to achieve a        gravimetric energy density of >200 Wh/kg. In most cases, the        anode active material mass loading of the electrodes (areal        density) is significantly lower than 25 mg/cm² and the apparent        volume density or tap density of the active material is        typically less than 1.2 g/cm³ even for relatively large        particles of graphite. The cathode active material mass loading        of the electrodes (areal density) is significantly lower than 45        mg/cm² for lithium metal oxide-type inorganic materials and        lower than 15 mg/cm² for organic or polymer materials. In        addition, there are so many other non-active materials (e.g.        conductive additive and resin binder) that add additional        weights and volumes to the electrode without contributing to the        cell capacity. These low areal densities and low volume        densities result in relatively low gravimetric energy density        and low volumetric energy density.    -   3) The conventional process requires dispersing electrode active        materials (anode active material and cathode active material) in        a liquid solvent (e.g. NMP) to make a slurry and, upon coating        on a current collector surface, the liquid solvent has to be        removed to dry the electrode layer. Once the anode and cathode        layers, along with a separator layer, are laminated together and        packaged in a housing to make a battery cell, one then injects a        liquid electrolyte into the cell. In actuality, one makes the        two electrodes wet, then makes the electrodes dry, and finally        makes them wet again. Such a dry-wet-dry-wet process is not a        good process at all.    -   4) Current lithium-ion batteries still suffer from a relatively        low gravimetric energy density and low volumetric energy        density. Commercially available lithium-ion batteries exhibit a        gravimetric energy density of approximately 150-220 Wh/kg and a        volumetric energy density of 450-600 Wh/L.

In literature, the energy density data reported based on either theactive material weight alone or the electrode weight cannot directlytranslate into the energy densities of a practical battery cell ordevice. The “overhead weight” or weights of other device components(binder, conductive additive, current collectors, separator,electrolyte, and packaging) must also be taken into account. Theconvention production process results in the weight proportion of theanode active material (e.g. graphite or carbon) in a lithium-ion batterybeing typically from 12% to 17%, and that of the cathode active materialfrom 20% to 35% (for inorganic such as LiMn₂O₄) or from 7-15% (fororganic or polymer cathode materials).

The present invention provides a lithium battery or sodium battery cellhaving a high electrode thickness, high active material mass loading,low overhead weight and volume, high capacity, and high energy density.In certain embodiments, the invention provides an alkali metal cellcomprising: (a) a quasi-solid polymer cathode containing about 30% toabout 95% by volume of a cathode active material, about 5% to about 40%by volume of a first electrolyte containing an alkali salt dissolved ina solvent and an ion-conducting polymer dissolved in, dispersed in, orimpregnated by this solvent, and about 0.01% to about 30% by volume of aconductive additive wherein the conductive additive, containingconductive filaments, forms a 3D network of electron-conducting pathwayssuch that the quasi-solid electrode has an electrical conductivity fromabout 10⁻⁶ S/cm to about 300 S/cm (may be higher); (b) an anode (may bea conventional anode or a quasi-solid polymer electrode); and (c) anion-conducting membrane or porous separator disposed between the anodeand the quasi-solid cathode; wherein said quasi-solid cathode has athickness no less than 200 μm. The quasi-solid polymer cathodepreferably contains a cathode active material mass loading no less than10 mg/cm², preferably no less than 15 mg/cm², further preferably no lessthan 25 mg/cm², more preferably no less than 35 mg/cm², still morepreferably no less than 45 mg/cm², and most preferably greater than 65mg/cm².

In this cell, the anode may also contain a quasi-solid polymer anodecontaining about 30% to about 95% by volume of an anode active material,about 5% to about 40% by volume of a second electrolyte containing analkali salt dissolved in a solvent and an ion-conducting polymerdissolved in, dispersed in, or impregnated by this solvent, and about0.01% to about 30% by volume of a conductive additive wherein saidconductive additive, containing conductive filaments, forms a 3D networkof electron-conducting pathways such that the quasi-solid electrode hasan electrical conductivity from about 10⁻⁶ S/cm to about 300 S/cm;wherein said quasi-solid anode has a thickness no less than 200 Thequasi-solid anode preferably contains an anode active material massloading no less than 10 mg/cm², preferably no less than 15 mg/cm²,further preferably no less than 25 mg/cm², more preferably no less than35 mg/cm², still more preferably no less than 45 mg/cm², and mostpreferably greater than 65 mg/cm². The first electrolyte may be the sameas or different from the second electrolyte in composition andstructure.

In some embodiments, the alkali metal battery contains a quasi-solidpolymer anode, but a conventional cathode.

The present invention also provides a method of producing an alkalimetal battery. In certain embodiments, the method comprises:

(a) combining a quantity of an active material (an anode active materialor a cathode active material), a quantity of a quasi-solid polymerelectrolyte (containing a polymer and a alkali metal salt dissolved in asolvent), and a conductive additive to form a deformable andelectrically conductive electrode material, wherein the conductiveadditive, containing conductive filaments, forms a 3D network ofelectron-conducting pathways; (These conductive filaments, such ascarbon nanotubes and graphene sheets, are a mass of randomly aggregatedfilaments prior to being mixed with particles of an active material andan electrolyte. The mixing procedure involves dispersing theseconductive filaments in a highly viscous electrolyte containingparticles of an active material. This will be further discussed in latersections.)

(b) forming the electrode material into a quasi-solid electrode, whereinthe forming step includes deforming the electrode material into anelectrode shape without interrupting the 3D network ofelectron-conducting pathways such that the electrode maintains anelectrical conductivity no less than 10⁻⁶ S/cm (preferably no less than10⁻⁵ S/cm, more preferably no less than 10⁻⁴ S/cm, further preferably noless than 10⁻³ S/cm, still more preferably and typically no less than10⁻² S/cm, even more typically and preferably no less than 10⁻¹ S/cm,and further more typically and preferably no less than 1 S/cm; up to 300S/cm was observed);

(c) forming a second electrode (the second electrode may be aquasi-solid polymer electrode or a conventional electrode); and

(d) forming an alkali metal cell by combining the quasi-solid electrodeand the second electrode having an ion-conducting separator disposedbetween the two electrodes.

As illustrated in FIG. 1(C), one preferred embodiment of the presentinvention is an alkali metal-ion cell having a conductive quasi-solidpolymer anode 236, a conductive quasi-solid polymer cathode 238, and aporous separator 240 (or ion-permeable membrane) that electronicallyseparates the anode and the cathode. These three components aretypically encased in a protective housing (not shown), which typicallyhas an anode tab (terminal) connected to the anode and a cathode tab(terminal) connected to the cathode. These tabs are for connecting tothe external load (e.g. an electronic device to be powered by thebattery). In this particular embodiment, the quasi-solid polymer anode236 contains an anode active material (e.g. particles of Si or hardcarbon, not shown in FIG. 1(C)), an electrolyte phase (typicallycontaining a lithium salt or sodium salt dissolved in a solvent and anion-conducting polymer dissolved in, dispersed in, or impregnated bythis solvent); also not shown in FIG. 1(C)), and a conductive additive(containing conductive filaments) that forms a 3D network ofelectron-conducting pathways 244. Similarly, the quasi-solid polymercathode contains a cathode active material, an electrolyte, and aconductive additive (containing conductive filaments) that forms a 3Dnetwork of electron-conducting pathways 242.

Another preferred embodiment of the present invention, as illustrated inFIG. 1(D), is an alkali metal cell having an anode composed of a lithiumor sodium metal coating/foil 282 deposited/attached to a currentcollector 280 (e.g. Cu foil), a quasi-solid cathode 284, and a separatoror ion-conducting membrane 282. The quasi-solid polymer cathode 284contains a cathode active material 272 (e.g. particles of LiCoO₂), anelectrolyte phase 274 (typically containing a lithium salt or sodiumsalt dissolved in a solvent and an ion-conducting polymer dissolved in,dispersed in, or impregnated by this solvent), and a conductive additivephase (containing conductive filaments) that forms a 3D network 270 ofelectron-conducting pathways. The present invention also includes alithium-ion capacitor and a sodium-ion capacitor.

The electrolyte is preferably a quasi-solid polymer electrolytecontaining a lithium salt or sodium salt and a polymer dissolved in asolvent with a combined salt/polymer concentration no less than 1.5 M,preferably greater than 2.5 M, more preferably greater than 3.5 M,further preferably greater than 5 M, still more preferably greater than7 M, and even more preferably greater than 10 M. In certain embodiments,the electrolyte is a quasi-solid polymer electrolyte containing apolymer and a lithium salt or sodium salt dissolved in a liquid solventwith a combined salt/polymer concentration from 3.0 M to 14 M. Thechoices of lithium salt or sodium salt and the solvent are furtherdiscussed in later sections.

In some embodiments, the electrolyte contains a lithium ion-conductingor sodium ion-conducting polymer selected from poly(ethylene oxide)(PEO, having a molecular weight lower than 1×10⁶ g/mole), polypropyleneoxide (PPO), poly(acrylonitrile) (PAN), poly(methyl methacrylate)(PMMA), poly(vinylidene fluoride) (PVdF), Poly bis-methoxyethoxyethoxide-phosphazenex, polyvinyl chloride, polydimethylsiloxane,poly(vinylidene fluoride)-hexafluoropropylene (PVDF-HFP), a sulfonatedderivative thereof, a sulfonated polymer, or a combination thereof.Sulfonation is herein found to impart improved lithium ion conductivityto a polymer. A PEO molecular weight higher than 1×10⁶ g/mole typicallymakes PEO difficult to get dissolved or dispersed in a solvent.

Typically, this ion-conducting polymer does not form a matrix(continuous phase) in the electrode. Rather, the polymer is dissolved ina solvent as a solution phase or dispersed as a discrete phase in asolvent matrix. The resulting electrolyte is a quasi-solid polymerelectrolyte; it is not a liquid electrolyte and not a solid electrolyte.

The ion-conducting polymer may be selected from the group consisting ofpoly(perfluoro sulfonic acid), sulfonated polytetrafluoroethylene,sulfonated perfluoroalkoxy derivatives of polytetrafluoroethylene,sulfonated polysulfone, sulfonated poly(ether ketone), sulfonated poly(ether ether ketone), sulfonated polystyrene, sulfonated polyimide,sulfonated styrene-butadiene copolymers, sulfonated polychloro-trifluoroethylene (PCTFE), sulfonated perfluoroethylene-propylenecopolymer (FEP), sulfonated ethylene-chlorotrifluoroethylene copolymer(ECTFE), sulfonated polyvinylidenefluoride (PVDF), sulfonated copolymersof polyvinylidenefluoride with hexafluoropropene andtetrafluoroethylene, sulfonated copolymers of ethylene andtetrafluoroethylene (ETFE), sulfonated polybenzimidazole (PBI), theirchemical derivatives, copolymers, blends and combinations thereof. Wehave surprisingly observed that these sulfonated polymers are bothlithium ion-conducting and sodium ion-conducting.

Both the quasi-solid anode and the quasi-solid cathode preferably have athickness greater than 200 μm (preferably greater than 300 μm, morepreferably greater than 400 μm, further preferably greater than 500 μm,still more preferably greater than 800 μm, further preferably greaterthan 1 mm, and can be greater than 5 mm, 1 cm, or thicker. There is notheoretical limitation on the presently invented electrode thickness. Inthe invented cells, the anode active material typically constitutes anelectrode active material loading no less than 20 mg/cm² (more typicallyand preferably no less than 25 mg/cm² and more preferably no less than30 mg/cm²) in the anode. The cathode active material constitutes anelectrode active material mass loading no less than 45 mg/cm² (typicallyand preferably greater than 50 mg/cm² and more preferably greater than60 mg/cm²) for an inorganic material as the cathode active material (noless than 25 mg/cm² for an organic or polymeric cathode activematerial).

In such configurations (FIG. 1(C) to FIG. 1(D)), the electrons only haveto travel a short distance (e.g. a few micrometers or less) before theyare collected by the conductive filaments that constitute the 3D networkof electron-conducting pathways and are present everywhere throughoutthe entire quasi-solid polymer electrode (an anode or cathode).Additionally, all electrode active material particles are pre-dispersedin an electrolyte solvent (no wettability issue), eliminating theexistence of dry pockets commonly present in an electrode prepared bythe conventional process of wet coating, drying, packing, andelectrolyte injection. Thus, the presently invented process or methodhas a totally unexpected advantage over the conventional battery cellproduction process.

These conductive filaments (such as carbon nanotubes and graphenesheets), as supplied, are originally a mass of randomly aggregatedfilaments prior to being mixed with particles of an active material andan electrolyte. The mixing procedure involves dispersing theseconductive filaments in a highly viscous, solid-like electrolytecontaining particles of an active material. This is not a trivial taskas one might think. The dispersion of nano materials (particularly nanofilament materials, such as carbon nanotubes, carbon nano-fibers, andgraphene sheets) in a highly flowable (non-viscous) liquid has beenknown to be notoriously difficult, let alone in a highly viscousquasi-solid, such as an electrolyte containing a high loading of anactive material (e.g. solid particles, such as Si nano particles for theanode and lithium cobalt oxide for the cathode). This problem is furtherexacerbated, in some preferred embodiments, by the notion that theelectrolyte itself is a quasi-solid polymer electrolyte, containing ahigh concentration of lithium salt or sodium salt and a polymer in asolvent.

In some preferred embodiments, the electrolyte contains a polymer and analkali metal salt (lithium salt and/or sodium salt) dissolved in anorganic or ionic liquid solvent with a combined alkali metalsalt/polymer concentration sufficiently high so that the electrolyteexhibits a vapor pressure less than 0.01 kPa or less than 0.6 (60%) ofthe vapor pressure of the solvent alone (when measured at 20° C.), aflash point at least 20 degrees Celsius higher than a flash point of thefirst organic liquid solvent alone (when no lithium salt is present), aflash point higher than 150° C., or no detectable flash point at all.

Most surprising and of tremendous scientific and technologicalsignificance is our discovery that the flammability of any volatileorganic solvent can be effectively suppressed provided that asufficiently high amount of an alkali metal salt and a polymer is addedto and dissolved in this organic solvent to form a solid-like orquasi-solid polymer electrolyte. In general, such a quasi-solid polymerelectrolyte exhibits a vapor pressure less than 0.01 kPa and often lessthan 0.001 kPa (when measured at 20° C.) and less than 0.1 kPa and oftenless than 0.01 kPa (when measured at 100° C.). (The vapor pressures ofthe corresponding neat solvent, without any alkali metal salt and/or apolymer dissolved therein, are typically significantly higher.) In manycases featuring the quasi-solid polymer electrolyte, the vapor moleculesare practically too few to be detected.

A highly significant observation is that the high solubility of thealkali metal salt and a polymer combined in an otherwise highly volatilesolvent (a large molecular ratio or molar fraction of alkali metalsalt/polymer chain segments, typically >0.2, more typically >0.3, andoften >0.4 or even >0.5) can dramatically curtail the amount of volatilesolvent molecules that can escape into the vapor phase in athermodynamic equilibrium condition. In many cases, this has effectivelyprevented the flammable solvent gas molecules from initiating a flameeven at an extremely high temperature (e.g. using a torch). The flashpoint of the quasi-solid polymer electrolyte is typically at least 20degrees (often >50 or >100 degrees) higher than the flash point of theneat organic solvent alone. In most of the cases, either the flash pointis higher than 150° C. or no flash point can be detected. Theelectrolyte just would not catch on fire. Furthermore, any accidentallyinitiated flame does not sustain for longer than a few seconds. This isa highly significant discovery, considering the notion that fire andexplosion concern has been a major impediment to widespread acceptanceof battery-powered electric vehicles. This new technology couldsignificantly help accelerate the emergence of a vibrant EV industry.

There has been no previous study reported on the vapor pressure ofultra-high concentration battery electrolytes (with a high molecularfraction, e.g. >0.2 or >0.3, of alkali metal salt/polymer chain segmentsor combined concentration approximately >2.5 M or 3.5 M) for safetyconsiderations. This is truly unexpected and of utmost technological andscientific significance.

We have further unexpectedly discovered that the presence of a 3Dnetwork of electron-conducting pathways, constituted by the conductingnano-filaments, acts to further reduce the threshold concentration ofthe alkali metal salt that is required for achieving critical vaporpressure suppression.

Another surprising element of the present invention is the notion thatwe are able to dissolve a high concentration of an alkali metal salt anda select ion-conducting polymer in just about every type of commonlyused battery-grade organic solvent to form a quasi-solid polymerelectrolyte suitable for use in a rechargeable alkali metal battery.Expressed in a more easily recognizable term, this concentration istypically greater than 2.5 M (mole/liter), more typically and preferablygreater than 3.5 M, still more typically and preferably greater than 5M, further more preferably greater than 7 M, and most preferably greaterthan 10 M. With a salt/polymer concentration no less than 2.5 M, theelectrolyte is no longer a liquid electrolyte; instead, it is aquasi-solid electrolyte. In the art of lithium or sodium battery, such ahigh concentration of alkali metal salt in a solvent has not beengenerally considered possible, nor desirable. However, we have foundthat these quasi-solid polymer electrolytes are surprisingly goodelectrolytes for both lithium and sodium batteries in terms ofsignificantly improved safety (non-flammability), improved energydensity, and improved power density.

In addition to the non-flammability and high alkali metal iontransference numbers as discussed above, there are several additionalbenefits associated with using the presently invented quasi-solidpolymer electrolytes. As one example, the quasi-solid polymerelectrolyte, when implemented at least in the anode, can significantlyenhance cyclic and safety performance of rechargeable alkali metalbatteries through effective suppression of dendrite growth. It isgenerally accepted that dendrites start to grow in the non-aqueousliquid electrolyte when the anion is depleted in the vicinity of theelectrode where plating occurs. In the ultrahigh concentrationelectrolyte, there is a mass of anions to keep the balance of cations(Li⁺ or Na⁺) and anions near metallic lithium or sodium anode. Further,the space charge created by anion depletion is minimal, which is notconducive to dendrite growth. Furthermore, due to both ultrahigh Li orNa salt concentration and high Li-ion or Na-ion transference number, thequasi-solid polymer electrolyte provides a large amount of availablelithium-ion or sodium-ion flux and raises the lithium or sodium ionicmass transfer rate between the electrolyte and the lithium or sodiumelectrode, thereby enhancing the lithium or sodium deposition uniformityand dissolution during charge/discharge processes. Additionally, thelocal high viscosity induced by a high concentration will increase thepressure from the electrolyte to inhibit dendrite growth, potentiallyresulting in a more uniform deposition on the surface of the anode. Thehigh viscosity could also limit anion convection near the depositionarea, promoting more uniform deposition of sodium ions. Same reasoningis applicable to lithium metal batteries. These reasons, separately orin combination, are believed to be responsible for the notion that nodendrite-like feature has been observed with any of the large number ofrechargeable alkali metal cells that we have investigated thus far.

Furthermore, a skilled artisan in the field of chemistry or materialsscience would have anticipated that such a high salt/polymerconcentration should make the electrolyte behave like a solid with anextremely high viscosity and, hence, this electrolyte should not beamenable to fast diffusion of alkali metal ions therein. Consequently,the artisan would have expected that an alkali metal battery containingsuch a solid-like polymer electrolyte would not and could not exhibit ahigh capacity at a high charge-discharge rate or under a high currentdensity condition (i.e. the battery should have a poor rate capability).Contrary to these expectations by a person of ordinary skills or evenexceptional skills in the art, all the alkali metal cells containingsuch a quasi-solid polymer electrolyte deliver high energy density andhigh power density for a long cycle life. It appears that thequasi-solid polymer electrolytes as herein invented and disclosed areconducive to facile alkali metal ion transport. This surprisingobservation is likely due to two major factors: one related to theinternal structure of the electrolyte and the other related to a highNa⁺ or Li⁺ ion transference number (TN).

Not wishing to be bound by theory, but one can visualize the internalstructure of three fundamentally different types of electrolytes byreferring to FIG. 2(A) to FIG. 2(C). FIG. 2(A) schematically shows theclosely packed, highly ordered structure of a typical solid electrolyte,wherein there is little free volume for diffusion of alkali metal ions.Migration of any ions in such a crystal structure is very difficult,leading to an extremely low diffusion coefficient (10⁻¹⁶ to 10⁻¹²cm²/sec) and extremely low ion conductivity (typically from 10⁻⁷ S/cm to10⁻⁴ S/cm). In contrast, as schematically shown in FIG. 2(B), theinternal structure of liquid electrolyte is totally amorphous, havinglarge fractions of free volume through which cations (e.g. or Li⁺ orNa⁺) can easily migrate, leading to a high diffusion coefficient (10⁻⁸to 10⁻⁶ cm²/sec) and high ion conductivity (typically from 10⁻³ S/cm to10⁻² S/cm). However, liquid electrolyte containing a low concentrationof alkali metal salt is flammable and prone to dendrite formation,posing fire and explosion danger. Schematically shown in FIG. 2(C) isthe randomized or amorphous structure of a quasi-solid polymerelectrolyte having solvent molecules separating salt species and polymerchain segments to produce amorphous zones for easy migration of free(un-clustered) cations. Such a structure is amenable to achieving a highion conductivity value (typically 10⁻⁴ S/cm to 8×10⁻³ S/cm), yet stillmaintaining non-flammability. There are relatively few solvent moleculesand these molecules are being retained (prevented from vaporizing) byoverwhelmingly large numbers of salt species, polymer chain segments,and the network of conducting filaments.

In a preferred embodiment, the anode active material is a prelithiatedor pre-sodiated version of graphene sheets selected from pristinegraphene, graphene oxide, reduced graphene oxide, graphene fluoride,graphene chloride, graphene bromide, graphene iodide, hydrogenatedgraphene, nitrogenated graphene, chemically functionalized graphene, ora combination thereof. The starting graphitic material for producing anyone of the above graphene materials may be selected from naturalgraphite, artificial graphite, meso-phase carbon, meso-phase pitch,meso-carbon micro-bead, soft carbon, hard carbon, coke, carbon fiber,carbon nano-fiber, carbon nano-tube, or a combination thereof. Graphenematerials are also a good conductive additive for both the anode andcathode active materials of a lithium battery.

The constituent graphene planes of a graphite crystallite in a naturalor artificial graphite particle can be exfoliated and extracted orisolated to obtain individual graphene sheets of hexagonal carbon atoms,which are single-atom thick, provided the inter-planar van der Waalsforces can be overcome. One process is illustrated in FIG. 4. Anisolated, individual graphene plane of carbon atoms is commonly referredto as single-layer graphene. A stack of multiple graphene planes bondedthrough van der Waals forces in the thickness direction with aninter-graphene plane spacing of approximately 0.3354 nm is commonlyreferred to as a multi-layer graphene. A multi-layer graphene platelethas up to 300 layers of graphene planes (<100 nm in thickness), but moretypically up to 30 graphene planes (<10 nm in thickness), even moretypically up to 20 graphene planes (<7 nm in thickness), and mosttypically up to 10 graphene planes (commonly referred to as few-layergraphene in scientific community). Single-layer graphene and multi-layergraphene sheets are collectively called “nano graphene platelets”(NGPs). Graphene sheets/platelets (collectively, NGPs) are a new classof carbon nano material (a 2-D nano carbon) that is distinct from the0-D fullerene, the 1-D CNT or CNF, and the 3-D graphite. For the purposeof defining the claims and as is commonly understood in the art, agraphene material (isolated graphene sheets) is not (and does notinclude) a carbon nanotube (CNT) or a carbon nano-fiber (CNF).

In one process, graphene materials are obtained by intercalating naturalgraphite particles with a strong acid and/or an oxidizing agent toobtain a graphite intercalation compound (GIC) or graphite oxide (GO),as illustrated in FIG. 5. The presence of chemical species or functionalgroups in the interstitial spaces between graphene planes in a GIC or GOserves to increase the inter-graphene spacing (d₀₀₂, as determined byX-ray diffraction), thereby significantly reducing the van der Waalsforces that otherwise hold graphene planes together along the c-axisdirection. The GIC or GO is most often produced by immersing naturalgraphite powder in a mixture of sulfuric acid, nitric acid (an oxidizingagent), and another oxidizing agent (e.g. potassium permanganate orsodium perchlorate). The resulting GIC is actually some type of graphiteoxide (GO) particles if an oxidizing agent is present during theintercalation procedure. This GIC or GO is then repeatedly washed andrinsed in water to remove excess acids, resulting in a graphite oxidesuspension or dispersion, which contains discrete and visuallydiscernible graphite oxide particles dispersed in water. In order toproduce graphene materials, one can follow one of the two processingroutes after this rinsing step, briefly described below:

Route 1 involves removing water from the suspension to obtain“expandable graphite,” which is essentially a mass of dried GIC or driedgraphite oxide particles. Upon exposure of expandable graphite to atemperature in the range of typically 800-1,050° C. for approximately 30seconds to 2 minutes, the GIC undergoes a rapid volume expansion by afactor of 30-300 to form “graphite worms”, which are each a collectionof exfoliated, but largely un-separated graphite flakes that remaininterconnected.

In Route 1A, these graphite worms (exfoliated graphite or “networks ofinterconnected/non-separated graphite flakes”) can be re-compressed toobtain flexible graphite sheets or foils that typically have a thicknessin the range of 0.1 mm (100 μm)-0.5 mm (500 μm). Alternatively, one maychoose to use a low-intensity air mill or shearing machine to simplybreak up the graphite worms for the purpose of producing the so-called“expanded graphite flakes” which contain mostly graphite flakes orplatelets thicker than 100 nm (hence, not a nano material bydefinition).

In Route 1B, the exfoliated graphite is subjected to high-intensitymechanical shearing (e.g. using an ultrasonicator, high-shear mixer,high-intensity air jet mill, or high-energy ball mill) to form separatedsingle-layer and multi-layer graphene sheets (collectively called NGPs),as disclosed in US20050271574 (Dec. 8, 2005). Single-layer graphene canbe as thin as 0.34 nm, while multi-layer graphene can have a thicknessup to 100 nm, but more typically less than 10 nm (commonly referred toas few-layer graphene). Multiple graphene sheets or platelets may bemade into a sheet of NGP paper using a paper-making process. This sheetof NGP paper is an example of the porous graphene structure layerutilized in the presently invented process.

Route 2 entails ultrasonicating the graphite oxide suspension (e.g.graphite oxide particles dispersed in water) for the purpose ofseparating/isolating individual graphene oxide sheets from graphiteoxide particles. This is based on the notion that the inter-grapheneplane separation bas been increased from 0.3354 nm in natural graphiteto 0.6-1.1 nm in highly oxidized graphite oxide, significantly weakeningthe van der Waals forces that hold neighboring planes together.Ultrasonic power can be sufficient to further separate graphene planesheets to form fully separated, isolated, or discrete graphene oxide(GO) sheets. These graphene oxide sheets can then be chemically orthermally reduced to obtain “reduced graphene oxides” (RGO) typicallyhaving an oxygen content of 0.001%-10% by weight, more typically0.01%-5% by weight, most typically and preferably less than 2% by weightof oxygen.

For the purpose of defining the claims of the instant application, NGPsor graphene materials include discrete sheets/platelets of single-layerand multi-layer (typically less than 10 layers) pristine graphene,graphene oxide, reduced graphene oxide (RGO), graphene fluoride,graphene chloride, graphene bromide, graphene iodide, hydrogenatedgraphene, nitrogenated graphene, chemically functionalized graphene,doped graphene (e.g. doped by B or N). Pristine graphene has essentially0% oxygen. RGO typically has an oxygen content of 0.001%-5% by weight.Graphene oxide (including RGO) can have 0.001%-50% by weight of oxygen.Other than pristine graphene, all the graphene materials have 0.001%-50%by weight of non-carbon elements (e.g. O, H, N, B, F, Cl, Br, I, etc.).These materials are herein referred to as non-pristine graphenematerials.

Pristine graphene, in smaller discrete graphene sheets (typically 0.3 μmto 10 μm), may be produced by direct ultrasonication (also known asliquid phase exfoliation or production) or supercritical fluidexfoliation of graphite particles. These processes are well-known in theart.

The graphene oxide (GO) may be obtained by immersing powders orfilaments of a starting graphitic material (e.g. natural graphitepowder) in an oxidizing liquid medium (e.g. a mixture of sulfuric acid,nitric acid, and potassium permanganate) in a reaction vessel at adesired temperature for a period of time (typically from 0.5 to 96hours, depending upon the nature of the starting material and the typeof oxidizing agent used). As previously described above, the resultinggraphite oxide particles may then be subjected to thermal exfoliation orultrasonic wave-induced exfoliation to produce isolated GO sheets. TheseGO sheets can then be converted into various graphene materials bysubstituting —OH groups with other chemical groups (e.g. —Br, NH₂,etc.).

Fluorinated graphene or graphene fluoride is herein used as an exampleof the halogenated graphene material group. There are two differentapproaches that have been followed to produce fluorinated graphene: (1)fluorination of pre-synthesized graphene: This approach entails treatinggraphene prepared by mechanical exfoliation or by CVD growth withfluorinating agent such as XeF₂, or F-based plasmas; (2) Exfoliation ofmultilayered graphite fluorides. Both mechanical exfoliation and liquidphase exfoliation of graphite fluoride can be readily accomplished.

Interaction of F₂ with graphite at high temperature leads to covalentgraphite fluorides (CF)_(n) or (C₂F)_(n), while at low temperaturesgraphite intercalation compounds (GIC) C_(x)F (2≤x≤24) form. In (CF),carbon atoms are sp3-hybridized and thus the fluorocarbon layers arecorrugated consisting of trans-linked cyclohexane chairs. In (C₂F), onlyhalf of the C atoms are fluorinated and every pair of the adjacentcarbon sheets are linked together by covalent C—C bonds. Systematicstudies on the fluorination reaction showed that the resulting F/C ratiois largely dependent on the fluorination temperature, the partialpressure of the fluorine in the fluorinating gas, and physicalcharacteristics of the graphite precursor, including the degree ofgraphitization, particle size, and specific surface area. In addition tofluorine (F₂), other fluorinating agents may be used, although most ofthe available literature involves fluorination with F₂ gas, sometimes inpresence of fluorides.

For exfoliating a layered precursor material to the state of individuallayers or few-layers, it is necessary to overcome the attractive forcesbetween adjacent layers and to further stabilize the layers. This may beachieved by either covalent modification of the graphene surface byfunctional groups or by non-covalent modification using specificsolvents, surfactants, polymers, or donor-acceptor aromatic molecules.The process of liquid phase exfoliation includes ultra-sonic treatmentof a graphite fluoride in a liquid medium.

The nitrogenation of graphene can be conducted by exposing a graphenematerial, such as graphene oxide, to ammonia at high temperatures(200-400° C.). Nitrogenated graphene could also be formed at lowertemperatures by a hydrothermal method; e.g. by sealing GO and ammonia inan autoclave and then increased the temperature to 150-250° C. Othermethods to synthesize nitrogen doped graphene include nitrogen plasmatreatment on graphene, arc-discharge between graphite electrodes in thepresence of ammonia, ammonolysis of graphene oxide under CVD conditions,and hydrothermal treatment of graphene oxide and urea at differenttemperatures.

There is no restriction on the types of anode active materials orcathode active materials that can be used in practicing the instantinvention. Preferably, in the invented lithium cell, the anode activematerial absorbs lithium ions at an electrochemical potential of lessthan 1.0 volt (preferably less than 0.7 volts) above the Li/Li⁺ (i.e.relative to Li→Li⁺+e⁻ as the standard potential) when the battery ischarged. In one preferred embodiment, the anode active material of alithium battery is selected from the group consisting of: (a) Particlesof lithium metal or a lithium metal alloy; (b) Natural graphiteparticles, artificial graphite particles, meso-carbon microbeads (MCMB),carbon particles (including soft carbon and hard carbon), needle coke,carbon nanotubes, carbon nano-fibers, carbon fibers, and graphitefibers; (c) Silicon (Si), germanium (Ge), tin (Sn), lead (Pb), antimony(Sb), bismuth (Bi), zinc (Zn), aluminum (Al), nickel (Ni), cobalt (Co),manganese (Mn), titanium (Ti), iron (Fe), and cadmium (Cd); (d) Alloysor intermetallic compounds of Si, Ge, Sn, Pb, Sb, Bi, Zn, Al, or Cd withother elements, wherein said alloys or compounds are stoichiometric ornon-stoichiometric; (e) Oxides, carbides, nitrides, sulfides,phosphides, selenides, and tellurides of Si, Ge, Sn, Pb, Sb, Bi, Zn, Al,Fe, Ni, Co, Ti, Mn, or Cd, and their mixtures or composites; (f)Pre-lithiated versions thereof; (g) Pre-lithiated graphene sheets; andcombinations thereof.

In certain embodiments, the alkali metal cell is a sodium metal cell orsodium-ion cell and the active material is an anode active materialcontaining a sodium intercalation compound selected from petroleum coke,carbon black, amorphous carbon, activated carbon, hard carbon (carbonthat is difficult to graphitize), soft carbon (carbon that can bereadily graphitized), templated carbon, hollow carbon nanowires, hollowcarbon sphere, titanates, NaTi₂(PO₄)₃, Na₂Ti₃O₇, Na₂C₈H₄O₄, Na₂TP,Na_(x)TiO₂ (x=0.2 to 1.0), Na₂C₈H₄O₄, carboxylate based materials,C₈H₄Na₂O₄, C₈H₆O₄, C₈H₅NaO₄, C₈Na₂F₄O₄, C₁₀H₂Na₄O₈, C₁₄H₄O₆, C₁₄H₄Na₄O₈,or a combination thereof.

In certain embodiments, the alkali metal cell is a sodium metal cell orsodium-ion cell and the active material is an anode active materialselected from the group consisting of: (a) Particles of sodium metal ora sodium metal alloy; (b) Natural graphite particles, artificialgraphite particles, meso-carbon microbeads (MCMB), carbon particles,needle coke, carbon nanotubes, carbon nano-fibers, carbon fibers, andgraphite fibers; (c) Sodium-doped silicon (Si), germanium (Ge), tin(Sn), lead (Pb), antimony (Sb), bismuth (Bi), zinc (Zn), aluminum (Al),titanium (Ti), cobalt (Co), nickel (Ni), manganese (Mn), cadmium (Cd),and mixtures thereof; (d) Sodium-containing alloys or intermetalliccompounds of Si, Ge, Sn, Pb, Sb, Bi, Zn, Al, Ti, Co, Ni, Mn, Cd, andtheir mixtures; (e) Sodium-containing oxides, carbides, nitrides,sulfides, phosphides, selenides, tellurides, or antimonides of Si, Ge,Sn, Pb, Sb, Bi, Zn, Al, Fe, Ti, Co, Ni, Mn, Cd, and mixtures orcomposites thereof; (f) Sodium salts; and (g) Graphene sheets pre-loadedwith sodium ions; and combinations thereof.

A wide variety of cathode active materials can be used to practice thepresently invented lithium cell. The cathode active material typicallyis a lithium intercalation compound or lithium-absorbing compound thatis capable of storing lithium ions when the lithium battery isdischarged and releasing lithium ions into the electrolyte whenrec-charged. The cathode active material may be selected from aninorganic material, an organic or polymeric material, a metaloxide/phosphate/sulfide (most desired types of inorganic cathodematerials), or a combination thereof:

The group of metal oxide, metal phosphate, and metal sulfides consistingof lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide,lithium vanadium oxide, lithium transition metal oxide, lithium-mixedmetal oxide, lithium iron phosphate, lithium manganese phosphate,lithium vanadium phosphate, lithium mixed metal phosphates, transitionmetal sulfides, and combinations thereof. In particular, the lithiumvanadium oxide may be selected from the group consisting of VO₂,Li_(x)VO₂, V₂O₅, Li_(x)V₂O₅, V₃O₈, Li_(x)V₃O₈, Li_(x)V₃O₇, V₄O₉,Li_(x)V₄O₉, V₆O₁₃, Li_(x)V₆O₁₃, their doped versions, their derivatives,and combinations thereof, wherein 0.1<x<5. Lithium transition metaloxide may be selected from a layered compound LiMO₂, spinel compoundLiM₂O₄, olivine compound LiMPO₄, silicate compound Li₂MSiO₄, Tavoritecompound LiMPO₄F, borate compound LiMBO₃, or a combination thereof,wherein M is a transition metal or a mixture of multiple transitionmetals.

Other inorganic materials for use as a cathode active material may beselected from sulfur, sulfur compound, lithium polysulfide, transitionmetal dichalcogenide, a transition metal trichalcogenide, or acombination thereof. In particular, the inorganic material is selectedfrom TiS₂, TaS₂, MoS₂, NbSe₃, MnO₂, CoO₂, an iron oxide, a vanadiumoxide, or a combination thereof. These will be further discussed later.

In particular, the inorganic material may be selected from: (a) bismuthselenide or bismuth telluride, (b) transition metal dichalcogenide ortrichalcogenide, (c) sulfide, selenide, or telluride of niobium,zirconium, molybdenum, hafnium, tantalum, tungsten, titanium, cobalt,manganese, iron, nickel, or a transition metal; (d) boron nitride, or(e) a combination thereof.

The organic material or polymeric material may be selected fromPoly(anthraquinonyl sulfide) (PAQS), a lithium oxocarbon,3,4,9,10-perylenetetracarboxylic dianhydride (PTCDA),poly(anthraquinonyl sulfide), pyrene-4,5,9,10-tetraone (PYT),polymer-bound PYT, Quino(triazene), redox-active organic material,Tetracyanoquinodimethane (TCNQ), tetracyanoethylene (TCNE),2,3,6,7,10,11-hexamethoxytriphenylene (HMTP), poly(5-amino-1,4-dyhydroxyanthraquinone) (PADAQ), phosphazene disulfide polymer ([(NPS₂)₃]n),lithiated 1,4,5,8-naphthalenetetraol formaldehyde polymer,Hexaazatrinaphtylene (HATN), Hexaazatriphenylene hexacarbonitrile(HAT(CN)₆), 5-Benzylidene hydantoin, Isatine lithium salt, Pyromelliticdiimide lithium salt, tetrahydroxy-p-benzoquinone derivatives (THQLi₄),N,N′-diphenyl-2,3,5,6-tetraketopiperazine (PHP),N,N′-diallyl-2,3,5,6-tetraketopiperazine (AP),N,N′-dipropyl-2,3,5,6-tetraketopiperazine (PRP), a thioether polymer, aquinone compound, 1,4-benzoquinone, 5,7,12,14-pentacenetetrone (PT),5-amino-2,3-dihydro-1,4-dyhydroxy anthraquinone (ADDAQ),5-amino-1,4-dyhydroxy anthraquinone (ADAQ), calixquinone, Li₄C₆O₆,Li₂C₆O₆, Li₆C₆O₆, or a combination thereof.

The thioether polymer is selected fromPoly[methanetetryl-tetra(thiomethylene)] (PMTTM),Poly(2,4-dithiopentanylene) (PDTP), a polymer containingPoly(ethene-1,1,2,2-tetrathiol) (PETT) as a main-chain thioetherpolymers, a side-chain thioether polymer having a main-chain consistingof conjugating aromatic moieties, and having a thioether side chain as apendant, Poly(2-phenyl-1,3-dithiolane) (PPDT),Poly(1,4-di(1,3-dithiolan-2-yl)benzene) (PDDTB),poly(tetrahydrobenzodithiophene) (PTHBDT), poly[1,2,4,5-tetrakis(propylthio)benzene] (PTKPTB, or poly[3,4(ethylenedithio)thiophene](PEDTT).

The organic material may be selected from a phthalocyanine compoundselected from copper phthalocyanine, zinc phthalocyanine, tinphthalocyanine, iron phthalocyanine, lead phthalocyanine, nickelphthalocyanine, vanadyl phthalocyanine, fluorochromium phthalocyanine,magnesium phthalocyanine, manganous phthalocyanine, dilithiumphthalocyanine, aluminum phthalocyanine chloride, cadmiumphthalocyanine, chlorogallium phthalocyanine, cobalt phthalocyanine,silver phthalocyanine, a metal-free phthalocyanine, a chemicalderivative thereof, or a combination thereof.

The lithium intercalation compound or lithium-absorbing compound may beselected from a metal carbide, metal nitride, metal boride, metaldichalcogenide, or a combination thereof. Preferably, the lithiumintercalation compound or lithium-absorbing compound is selected from anoxide, dichalcogenide, trichalcogenide, sulfide, selenide, or tellurideof niobium, zirconium, molybdenum, hafnium, tantalum, tungsten,titanium, vanadium, chromium, cobalt, manganese, iron, or nickel in ananowire, nano-disc, nano-ribbon, or nano platelet form.

We have discovered that a wide variety of two-dimensional (2D) inorganicmaterials can be used as a cathode active material in the presentedinvented lithium battery prepared by the invented direct activematerial-electrolyte injection process. Layered materials represent adiverse source of 2D systems that can exhibit unexpected electronicproperties and good affinity to lithium ions. Although graphite is thebest known layered material, transition metal dichalcogenides (TMDs),transition metal oxides (TMOs), and a broad array of other compounds,such as BN, Bi₂Te₃, and Bi₂Se₃, are also potential sources of 2Dmaterials.

Preferably, the lithium intercalation compound or lithium-absorbingcompound is selected from nanodiscs, nanoplatelets, nano-coating, ornanosheets of an inorganic material selected from: (a) bismuth selenideor bismuth telluride, (b) transition metal dichalcogenide ortrichalcogenide, (c) sulfide, selenide, or telluride of niobium,zirconium, molybdenum, hafnium, tantalum, tungsten, titanium, cobalt,manganese, iron, nickel, or a transition metal; (d) boron nitride, or(e) a combination thereof; wherein the discs, platelets, or sheets havea thickness less than 100 nm. The lithium intercalation compound orlithium-absorbing compound may contain nanodiscs, nanoplatelets,nano-coating, or nanosheets of a compound selected from: (i) bismuthselenide or bismuth telluride, (ii) transition metal dichalcogenide ortrichalcogenide, (iii) sulfide, selenide, or telluride of niobium,zirconium, molybdenum, hafnium, tantalum, tungsten, titanium, cobalt,manganese, iron, nickel, or a transition metal; (iv) boron nitride, or(v) a combination thereof, wherein the discs, platelets, coating, orsheets have a thickness less than 100 nm.

In the rechargeable sodium cell, the cathode active material may containa sodium intercalation compound selected from NaFePO₄ (Sodium ironphosphate), Na_(0.7)FePO₄, Na_(1.5) VOPO₄F_(0.5), Na₃V₂(PO₄)₃,Na₃V2(PO₄)₂F₃, Na₂FePO₄F, NaFeF₃, NaVPO₄F, Na₃V₂(PO₄)₂F₃,Na_(1.5)VOPO₄F_(0.5), Na₃V₂(PO₄)₃, NaV₆O₁₅, Na_(x)VO₂, Na_(0.33)V₂O₅,Na_(x)CoO₂ (Sodium cobalt oxide), Na_(2/3)[Ni_(1/3)Mn_(2/3)]O₂,Na_(x)(Fe_(1/2)Mn_(1/2))O₂, Na_(x)MnO₂ (Sodium manganese bronze),Na_(0.44)MnO₂, Na_(0.44)MnO₂/C, Na₄Mn₉O₁₈, NaFe₂Mn(PO₄)₃, Na₂Ti₃O₇,Ni_(1/3)Mn_(1/3)Co_(1/3)O₂, Cu_(0.56)Ni_(0.44)HCF (Copper and nickelhexacyanoferrate), NiHCF (nickel hexacyanoferrate), Na_(x)CoO₂, NaCrO₂,Na₃Ti₂(PO₄)₃, NiCo₂O₄, Ni₃S₂/FeS₂, Sb₂O₄, Na₄Fe(CN)₆/C,NaV_(1-x)Cr_(x)PO₄F, Se_(y)S_(z) (Selenium and Selenium/Sulfur, z/y from0.01 to 100), Se (without S), Alluaudites, or a combination thereof.

Alternatively, the cathode active material may be selected from afunctional material or nano-structured material having an alkali metalion-capturing functional group or alkali metal ion-storing surface indirect contact with the electrolyte. Preferably, the functional groupreversibly reacts with an alkali metal ion, forms a redox pair with analkali metal ion, or forms a chemical complex with an alkali metal ion.The functional material or nanostructured material may be selected fromthe group consisting of (a) a nanostructured or porous disordered carbonmaterial selected from a soft carbon, hard carbon, polymeric carbon orcarbonized resin, mesophase carbon, coke, carbonized pitch, carbonblack, activated carbon, nanocellular carbon foam or partiallygraphitized carbon; (b) a nano graphene platelet selected from asingle-layer graphene sheet or multi-layer graphene platelet; (c) acarbon nanotube selected from a single-walled carbon nanotube ormulti-walled carbon nanotube; (d) a carbon nanofiber, nanowire, metaloxide nanowire or fiber, conductive polymer nanofiber, or a combinationthereof; (e) a carbonyl-containing organic or polymeric molecule; (f) afunctional material containing a carbonyl, carboxylic, or amine group;and combinations thereof.

The functional material or nano-structured material may be selected fromthe group consisting ofPoly(2,5-dihydroxy-1,4-benzoquinone-3,6-methylene), Na_(x)C₆O₆ (x=1-3),Na₂(C₆H₂O₄), Na₂C₈H₄O₄ (Na terephthalate), Na₂C₆H₄O₄(Litrans-trans-muconate), 3,4,9,10-perylenetetracarboxylicacid-dianhydride(PTCDA) sulfide polymer, PTCDA,1,4,5,8-naphthalene-tetracarboxylicacid-dianhydride (NTCDA),Benzene-1,2,4,5-tetracarboxylic dianhydride, 1,4,5,8-tetrahydroxyanthraquinon, Tetrahydroxy-p-benzoquinone, and combinations thereof.Desirably, the functional material or nano-structured material has afunctional group selected from —COOH, ═O, —NH₂, —OR, or —COOR, where Ris a hydrocarbon radical.

Non-graphene 2D nano materials, single-layer or few-layer (up to 20layers), can be produced by several methods: mechanical cleavage, laserablation (e.g. using laser pulses to ablate TMDs down to a singlelayer), liquid phase exfoliation, and synthesis by thin film techniques,such as PVD (e.g. sputtering), evaporation, vapor phase epitaxy, liquidphase epitaxy, chemical vapor epitaxy, molecular beam epitaxy (MBE),atomic layer epitaxy (ALE), and their plasma-assisted versions.

A wide range of electrolytes can be used for practicing the instantinvention. Most preferred are non-aqueous organic and/or ionic liquidelectrolytes. The non-aqueous electrolyte to be employed herein may beproduced by dissolving an electrolytic salt in a non-aqueous solvent.Any known non-aqueous solvent which has been employed as a solvent for alithium secondary battery can be employed. A non-aqueous solvent mainlyconsisting of a mixed solvent comprising ethylene carbonate (EC) and atleast one kind of non-aqueous solvent whose melting point is lower thanthat of aforementioned ethylene carbonate and whose donor number is 18or less (hereinafter referred to as a second solvent) may be preferablyemployed. This non-aqueous solvent is advantageous in that it is (a)stable against a negative electrode containing a carbonaceous materialwell developed in graphite structure; (b) effective in suppressing thereductive or oxidative decomposition of electrolyte; and (c) high inconductivity. A non-aqueous electrolyte solely composed of ethylenecarbonate (EC) is advantageous in that it is relatively stable againstdecomposition through a reduction by a graphitized carbonaceousmaterial. However, the melting point of EC is relatively high, 39 to 40°C., and the viscosity thereof is relatively high, so that theconductivity thereof is low, thus making EC alone unsuited for use as asecondary battery electrolyte to be operated at room temperature orlower. The second solvent to be used in a mixture with EC functions tomake the viscosity of the solvent mixture lower than that of EC alone,thereby promoting the ion conductivity of the mixed solvent.Furthermore, when the second solvent having a donor number of 18 or less(the donor number of ethylene carbonate is 16.4) is employed, theaforementioned ethylene carbonate can be easily and selectively solvatedwith lithium ion, so that the reduction reaction of the second solventwith the carbonaceous material well developed in graphitization isassumed to be suppressed. Further, when the donor number of the secondsolvent is controlled to not more than 18, the oxidative decompositionpotential to the lithium electrode can be easily increased to 4 V ormore, so that it is possible to manufacture a lithium secondary batteryof high voltage.

Preferable second solvents are dimethyl carbonate (DMC), methylethylcarbonate (MEC), diethyl carbonate (DEC), ethyl propionate, methylpropionate, propylene carbonate (PC), .gamma.-butyrolactone(.gamma.-BL), acetonitrile (AN), ethyl acetate (EA), propyl formate(PF), methyl formate (MF), toluene, xylene and methyl acetate (MA).These second solvents may be employed singly or in a combination of twoor more. More desirably, this second solvent should be selected fromthose having a donor number of 16.5 or less. The viscosity of thissecond solvent should preferably be 28 cps or less at 25° C.

The mixing ratio of the aforementioned ethylene carbonate in the mixedsolvent should preferably be 10 to 80% by volume. If the mixing ratio ofthe ethylene carbonate falls outside this range, the conductivity of thesolvent may be lowered or the solvent tends to be more easilydecomposed, thereby deteriorating the charge/discharge efficiency. Morepreferable mixing ratio of the ethylene carbonate is 20 to 75% byvolume. When the mixing ratio of ethylene carbonate in a non-aqueoussolvent is increased to 20% by volume or more, the solvating effect ofethylene carbonate to lithium ions will be facilitated and the solventdecomposition-inhibiting effect thereof can be improved.

Examples of preferred mixed solvent are a composition comprising EC andMEC; comprising EC, PC and MEC; comprising EC, MEC and DEC; comprisingEC, MEC and DMC; and comprising EC, MEC, PC and DEC; with the volumeratio of MEC being controlled within the range of 30 to 80%. Byselecting the volume ratio of MEC from the range of 30 to 80%, morepreferably 40 to 70%, the conductivity of the solvent can be improved.With the purpose of suppressing the decomposition reaction of thesolvent, an electrolyte having carbon dioxide dissolved therein may beemployed, thereby effectively improving both the capacity and cycle lifeof the battery. The electrolytic salts to be incorporated into anon-aqueous electrolyte may be selected from a lithium salt such aslithium perchlorate (LiClO₄), lithium hexafluorophosphate (LiPF₆),lithium borofluoride (LiBF₄), lithium hexafluoroarsenide (LiAsF₆),lithium trifluoro-metasulfonate (LiCF₃SO₃) and bis-trifluoromethylsulfonylimide lithium [LiN(CF₃SO₂)₂]. Among them, LiPF₆, LiBF₄ andLiN(CF₃SO₂)₂ are preferred. The content of aforementioned electrolyticsalts in the non-aqueous solvent is preferably 0.5 to 2.0 mol/l.

For sodium cells, the electrolyte (including non-flammable quasi-solidelectrolyte) may contain a sodium salt preferably selected from sodiumperchlorate (NaClO₄), sodium hexafluorophosphate (NaPF₆), sodiumborofluoride (NaBF₄), sodium hexafluoroarsenide, sodiumtrifluoro-metasulfonate (NaCF₃SO₃), bis-trifluoromethyl sulfonylimidesodium (NaN(CF₃SO₂)₂), an ionic liquid salt, or a combination thereof.

The ionic liquid is composed of ions only. Ionic liquids are low meltingtemperature salts that are in a molten or liquid state when above adesired temperature. For instance, a salt is considered as an ionicliquid if its melting point is below 100° C. If the melting temperatureis equal to or lower than room temperature (25° C.), the salt isreferred to as a room temperature ionic liquid (RTIL). The IL salts arecharacterized by weak interactions, due to the combination of a largecation and a charge-delocalized anion. This results in a low tendency tocrystallize due to flexibility (anion) and asymmetry (cation).

A typical and well-known ionic liquid is formed by the combination of a1-ethyl-3-methylimidazolium (EMI) cation and anN,N-bis(trifluoromethane)sulphonamide (TFSI) anion. This combinationgives a fluid with an ionic conductivity comparable to many organicelectrolyte solutions and a low decomposition propensity and low vaporpressure up to ˜300-400° C. This implies a generally low volatility andnon-flammability and, hence, a much safer electrolyte for batteries.

Ionic liquids are basically composed of organic ions that come in anessentially unlimited number of structural variations owing to thepreparation ease of a large variety of their components. Thus, variouskinds of salts can be used to design the ionic liquid that has thedesired properties for a given application. These include, among others,imidazolium, pyrrolidinium and quaternary ammonium salts as cations andbis(trifluoromethanesulphonyl) imide, bis(fluorosulphonyl)imide, andhexafluorophosphate as anions. Based on their compositions, ionicliquids come in different classes that basically include aprotic, proticand zwitterionic types, each one suitable for a specific application.

Common cations of room temperature ionic liquids (RTILs) include, butnot limited to, tetraalkylammonium, di-, tri-, andtetra-alkylimidazolium, alkylpyridinium, dialkyl-pyrrolidinium,dialkylpiperidinium, tetraalkylphosphonium, and trialkylsulfonium.Common anions of RTILs include, but not limited to, BF₄ ⁻, B(CN)₄ ⁻,CH₃BF₃ ⁻, CH2CHBF₃ ⁻, CF₃BF₃ ⁻, C₂F₅BF₃ ⁻, n-C₃F₇BF₃ ⁻, n-C₄F₉BF₃ ⁻, PF₆⁻, CF₃CO₂ ⁻, CF₃SO₃ ⁻, N(SO₂CF₃)₂ ⁻, N(COCF₃)(SO₂CF₃)⁻, N(SO₂F)₂ ⁻,N(CN)₂ ⁻, C(CN)₃ ⁻, SCN⁻, SeCN⁻, CuCl₂ ⁻, AlCl₄ ⁻, F(HF)_(2.3) ⁻, etc.Relatively speaking, the combination of imidazolium- or sulfonium-basedcations and complex halide anions such as AlCl₄ ⁻, BF₄ ⁻, CF₃CO₂ ⁻,CF₃SO₃ ⁻, NTf₂ ⁻, N(SO₂F)₂ ⁻, or F(HF)_(2.3) ⁻ results in RTILs withgood working conductivities.

RTILs can possess archetypical properties such as high intrinsic ionicconductivity, high thermal stability, low volatility, low (practicallyzero) vapor pressure, non-flammability, the ability to remain liquid ata wide range of temperatures above and below room temperature, highpolarity, high viscosity, and wide electrochemical windows. Theseproperties, except for the high viscosity, are desirable attributes whenit comes to using an RTIL as an electrolyte ingredient (a salt and/or asolvent) in a supercapacitor.

In what follows, we provide some examples of several different types ofanode active materials, cathode active materials, and ion-conductingpolymers to illustrate the best mode of practicing the instantinvention. Theses illustrative examples and other portions of instantspecification and drawings, separately or in combinations, are more thanadequate to enable a person of ordinary skill in the art to practice theinstant invention. However, these examples should not be construed aslimiting the scope of instant invention.

Example 1: Preparation of Graphene Oxide (GO) and Reduced Graphene Oxide(RGO) Nano Sheets from Natural Graphite Powder

Natural graphite from Huadong Graphite Co. (Qingdao, China) was used asthe starting material. GO was obtained by following the well-knownmodified Hummers method, which involved two oxidation stages. In atypical procedure, the first oxidation was achieved in the followingconditions: 1100 mg of graphite was placed in a 1000 mL boiling flask.Then, 20 g of K₂S₂O₈, 20 g of P₂O₅, and 400 mL of a concentrated aqueoussolution of H₂SO₄ (96%) were added in the flask. The mixture was heatedunder reflux for 6 hours and then let without disturbing for 20 hours atroom temperature. Oxidized graphite was filtered and rinsed withabundant distilled water until neutral pH. A wet cake-like material wasrecovered at the end of this first oxidation.

For the second oxidation process, the previously collected wet cake wasplaced in a boiling flask that contains 69 mL of a concentrated aqueoussolution of H₂SO₄ (96%). The flask was kept in an ice bath as 9 g ofKMnO₄ was slowly added. Care was taken to avoid overheating. Theresulting mixture was stirred at 35° C. for 2 hours (the sample colorturning dark green), followed by the addition of 140 mL of water. After15 min, the reaction was halted by adding 420 mL of water and 15 mL ofan aqueous solution of 30 wt % H₂O₂. The color of the sample at thisstage turned bright yellow. To remove the metallic ions, the mixture wasfiltered and rinsed with a 1:10 HCl aqueous solution. The collectedmaterial was gently centrifuged at 2700 g and rinsed with deionizedwater. The final product was a wet cake that contained 1.4 wt % of GO,as estimated from dry extracts. Subsequently, liquid dispersions of GOplatelets were obtained by lightly sonicating wet-cake materials, whichwere diluted in deionized water.

Surfactant-stabilized RGO (RGO-BS) was obtained by diluting the wet-cakein an aqueous solution of surfactants instead of pure water. Acommercially available mixture of cholate sodium (50 wt. %) anddeoxycholate sodium (50 wt. %) salts provided by Sigma Aldrich was used.The surfactant weight fraction was 0.5 wt. %. This fraction was keptconstant for all samples. Sonication was performed using a BransonSonifier S-250A equipped with a 13 mm step disruptor horn and a 3 mmtapered micro-tip, operating at a 20 kHz frequency. For instance, 10 mLof aqueous solutions containing 0.1 wt. % of GO was sonicated for 10 minand subsequently centrifuged at 2700 g for 30 min to remove anynon-dissolved large particles, aggregates, and impurities. Chemicalreduction of as-obtained GO to yield RGO was conducted by following themethod, which involved placing 10 mL of a 0.1 wt. % GO aqueous solutionin a boiling flask of 50 mL. Then, 10 μL of a 35 wt. % aqueous solutionof N₂H₄ (hydrazine) and 70 mL of a 28 wt. % of an aqueous solution ofNH₄OH (ammonia) were added to the mixture, which was stabilized bysurfactants. The solution was heated to 90° C. and refluxed for 1 h. ThepH value measured after the reaction was approximately 9. The color ofthe sample turned dark black during the reduction reaction.

RGO was used as a conductive additive in either or both of the anode andcathode active material in certain lithium batteries presently invented.Pre-lithiated RGO (e.g. RGO+lithium particles or RGO pre-deposited withlithium coating) was also used as an anode active material in selectedlithium-ion cells.

For comparison purposes, slurry coating and drying procedures wereconducted to produce conventional electrodes. One anode and one cathode,and a separator disposed between the two electrodes, were then assembledand encased in an Al-plastic laminated packaging envelop, followed byliquid electrolyte injection to form a prior art lithium battery cell.

Example 2: Preparation of Pristine Graphene Sheets (Essentially 0%Oxygen)

Recognizing the possibility of the high defect population in GO sheetsacting to reduce the conductivity of individual graphene plane, wedecided to study if the use of pristine graphene sheets (non-oxidizedand oxygen-free, non-halogenated and halogen-free, etc.) can lead to aconductive additive having a high electrical and thermal conductivity.Pre-lithiated pristine graphene was also used as an anode activematerial. Pristine graphene sheets were produced by using the directultrasonication or liquid-phase production process.

In a typical procedure, five grams of graphite flakes, ground toapproximately 20 μm or less in sizes, were dispersed in 1,000 mL ofdeionized water (containing 0.1% by weight of a dispersing agent, Zonyl®FSO from DuPont) to obtain a suspension. An ultrasonic energy level of85 W (Branson S450 Ultrasonicator) was used for exfoliation, separation,and size reduction of graphene sheets for a period of 15 minutes to 2hours. The resulting graphene sheets are pristine graphene that havenever been oxidized and are oxygen-free and relatively defect-free.Pristine graphene is essentially free from any non-carbon elements.

Pristine graphene sheets, as a conductive additive, along with an anodeactive material (or cathode active material in the cathode) were thenincorporated in a battery using both the presently invented procedure ofslurry injection into foam pores and conventional procedure of slurrycoating, drying and layer laminating. Both lithium-ion batteries andlithium metal batteries (injection into cathode only) were investigated.

Example 3: Preparation of Prelithiated Graphene Fluoride Sheets as anAnode Active Material of a Lithium-Ion Battery

Several processes have been used by us to produce GF, but only oneprocess is herein described as an example. In a typical procedure,highly exfoliated graphite (HEG) was prepared from intercalated compoundC₂F.xClF₃. HEG was further fluorinated by vapors of chlorine trifluorideto yield fluorinated highly exfoliated graphite (FHEG). Pre-cooledTeflon reactor was filled with 20-30 mL of liquid pre-cooled ClF₃, thereactor was closed and cooled to liquid nitrogen temperature. Then, nomore than 1 g of HEG was put in a container with holes for ClF₃ gas toaccess and situated inside the reactor. In 7-10 days a gray-beigeproduct with approximate formula C₂F was formed.

Subsequently, a small amount of FHEG (approximately 0.5 mg) was mixedwith 20-30 mL of an organic solvent (methanol and ethanol, separately)and subjected to an ultrasound treatment (280 W) for 30 min, leading tothe formation of homogeneous yellowish dispersions. Upon removal ofsolvent, the dispersion became a brownish powder. The graphene fluoridepowder was mixed with surface-stabilized lithium powder in a liquidelectrolyte, allowing for pre-lithiation to occur.

Example 4: Some Examples of Preferred Salts, Solvents, and Polymers forForming Quasi-Solid Polymer Electrolytes

Preferred sodium metal salts include: sodium perchlorate (NaClO₄),sodium hexafluorophosphate (NaPF₆), sodium borofluoride (NaBF₄), sodiumhexafluoroarsenide, potassium hexafluoroarsenide, sodiumtrifluoro-metasulfonate (NaCF₃SO₃), and bis-trifluoromethylsulfonylimide sodium (NaN(CF₃SO₂)₂). The following are good choices forlithium salts that tend to be dissolved well in selected organic orionic liquid solvents: lithium borofluoride (LiBF₄), lithiumtrifluoro-metasulfonate (LiCF₃SO₃), lithium bis-trifluoromethylsulfonylimide (LiN(CF₃SO₂)₂ or LITFSI), lithium bis(oxalato)borate(LiBOB), lithium oxalyldifluoroborate (LiBF₂C₂O₄), and lithiumbisperfluoroethy-sulfonylimide (LiBETI). A good electrolyte additive forhelping to stabilize Li metal is LiNO₃. Particularly useful ionicliquid-based lithium salts include: lithium bis(trifluoromethanesulfonyl)imide (LiTFSI).

Preferred organic liquid solvents include: ethylene carbonate (EC),dimethyl carbonate (DMC), methylethyl carbonate (MEC), diethyl carbonate(DEC), propylene carbonate (PC), acetonitrile (AN), vinylene carbonate(VC), allyl ethyl carbonate (AEC), 1,3-dioxolane (DOL),1,2-dimethoxyethane (DME), tetraethylene glycol dimethylether (TEGDME),Poly(ethylene glycol) dimethyl ether (PEGDME), diethylene glycol dibutylether (DEGDBE), 2-ethoxyethyl ether (EEE), hydrofloroether (e.g. TPTP),sulfone, and sulfolane.

Preferred ionic liquid solvents may be selected from a room temperatureionic liquid (RTIL) having a cation selected from tetraalkylammonium,di-alkylimidazolium, alkylpyridinium, dialkyl-pyrrolidinium, ordialkylpiperidinium. The counter anion is preferably selected from BF₄⁻, B(CN)₄ ⁻, CF₃CO₂ ⁻, CF₃SO₃ ⁻, N(SO₂CF₃)₂ ⁻, N(COCF₃)(SO₂CF₃)⁻, orN(SO₂F)₂ ⁻. Particularly useful ionic liquid-based solvents includeN-n-butyl-N-ethylpyrrolidinium bis(trifluoromethane sulfonyl)imide(BEPyTFSI), N-methyl-N-propylpiperidinium bis(trifluoromethylsulfonyl)imide (PP₁₃TFSI), and N,N-diethyl-N-methyl-N-(2-methoxyethyl)ammonium bis(trifluoromethylsulfonyl)imide.

Preferred lithium ion-conducting or sodium ion-conducting polymersinclude poly(ethylene oxide) (PEO, having a molecular weight lower than1×10⁶ g/mole), polypropylene oxide (PPO), poly(acrylonitrile) (PAN),poly(vinylidene fluoride)-hexafluoropropylene (PVDF-HFP) and sulfonatedpolymers. Preferred sulfonated polymers include poly(perfluoro sulfonicacid), sulfonated polytetrafluoroethylene, sulfonated polysulfone,sulfonated poly (ether ether ketone) (S-PEEK), and sulfonatedpolyvinylidenefluoride (S-PVDF).

Example 5: Vapor Pressure of Some Solvents and Corresponding Quasi-SolidPolymer Electrolytes with Various Sodium Salt Molecular Ratios

Vapor pressures of several solvents (DOL, DME, PC, AN, with or withoutan ionic liquid-based co-solvent, PP₁₃TFSI) before and after adding awide molecular ratio range of sodium salts, such as sodium borofluoride(NaBF₄), sodium perchlorate (NaClO₄), or sodium bis(trifluoromethanesulfonyl)imide (NaTFSI), along with PEO, were measured. The vaporpressure drops at a very high rate when the combined salt/polymerconcentration exceeds 2.3 M, and rapidly approaches a minimal oressentially zero when the combined concentration exceeds 3.0 M. With avery low vapor pressure, the vapor phase of the electrolyte eithercannot ignite or cannot sustain a flame for longer than 3 seconds onceinitiated.

Example 6: Flash Points and Vapor Pressure of Some Solvents andCorresponding Quasi-Solid Polymer Electrolytes with a Combined Sodium orLithium Salt/Polymer Concentration of 3.0M

The flash points and vapor pressures of several solvents and theirelectrolytes with a Na or Li salt/polymer concentration of 3 M arepresented in Table 1 below. It may be noted that, according to the OSHA(Occupational Safety & Health Administration) classification, any liquidwith a flash point below 38.7° C. is flammable. However, in order toensure safety, we have designed our quasi-solid polymer electrolytes toexhibit a flash point significantly higher than 38.7° C. (by a largemargin, e.g. at least increased by 50° and preferably above 150° C.).The data in Table 1 indicate that the addition of a combined alkalimetal salt/polymer concentration of 3.0M is normally sufficient to meetthese criteria (in many cases, 2.3 M is sufficient). All our quasi-solidpolymer electrolytes are not flammable.

TABLE 1 The flash points and vapor pressures of select solvents andtheir electrolytes. Flash Flash point (° C.) Vapor pressure Vaporpressure point with 3.0M (kPa) at 20° C., no (kPa) at 20° C. Chemical (°C.) concentration solute with 3.0M Acetone −17 — 24 kPa (240 hPa) —Ethanol 17 — — DOL (1,3-dioxolane) 1 84 (PEO + LiBF₄) 9.33 (70 Torr) 2.3DOL 1 182 (PEO + LiCF₃ 9.33 0.7 (PEO + LiCF₃ SO₃); 187 (PEO + SO₃); 0.5(PEO + NaCF₃SO₃) LiCF₃SO₃) DEC (diethyl carbonate) 33 >200 (PPO + 1.33(10 Torr) 0.03 (PPO + LiCF₃SO₃) LiCF₃SO₃) DMC (Dimethyl 18 190 (PAN +2.40 (18 Torr) 0.13 (PAN + carbonate) LiCF₃SO₃) LiCF₃SO₃) EMC (ethylmethyl 23 198 (PAN + 3.60 (27 Torr) 0.1(PAN + LiBOB) carbonate) LiBOB)EC (ethylene carbonate) 145 No flash point <0.0013 (0.02 Torr at 36.4°C.) <0.01 (LiBOB + PPO) (LiBOB + PPO) PC (propylene carbonate) 132 Noflash point 0.0173 (0.13 Torr) <0.01 (LiBOB + (LiBOB + PEO) PEO) γ-BL(gamma- 98 No flash point 0.20 (1.5 Torr) <0.01 (LiBOB + butyrolactone)(LiBOB + PEO) PEO) AN (Acetonitrile) 6 96 (PEO + LiBF₄) 9.71 (88.8 Torrat 25° C.) 1.1 (LiBF₄) 104 (PEONaBF₄) 0.75 (NaBF₄) EA (Ethyl acetate) +DOL −3 70 (S-PVDF LiBF₄) 9.73 0.7(S-PVDF LiBF₄) DME (1,2- −2 68 (PAN +LiPF₆) 6.40 (48 Torr) 1.6(PAN + LiPF₆) dimethoxyethane) 77 PAN + (NaPF₆)1.1(PAN + LiPF₆) VC (vinylene carbonate) 53.1 188 (S-PEEK + 11.98 (89.9Torr) 0.43 (S-PEEK LiPF₆) LiPF₆) TEGDME (tetraethylene 141 No flashpoint <0.0013 (<0.01 Torr) <0.001 glycol dimethylether) (LiPF₆) FEC(Fluoro ethylene 122 No flash point 0.021 <0.01 carbonate) (LiPF₆) IL(1-ethyl-3-methyl 283 No flash point — — imadazolium TFSI) (NaTFSI) *Asper OSHA (Occupational Safety & Health Administration) classification,any liquid with a flash point below 38.7° C. is flammable; **1 standardatmosphere = 101,325 Pa = 101.325 kPa = 1,013.25 hPa. 1 Torr = 133.3 Pa= 0.1333 kPa

Example 7: Alkali Metal Ion Transference Numbers in Several Electrolytes

The Na⁺ ion transference numbers of several types of electrolytes (e.g.(PEO+NaTFSI salt) in (EMImTFSI+DME) solvents) in relation to the lithiumsalt molecular ratio were studied and representative results aresummarized in FIG. 3(A) to FIG. 3(B). In general, the Na⁺ iontransference number in low salt concentration electrolytes decreaseswith increasing concentration from x=0 to x=0.2-0.30. However, beyondmolecular ratios of x=0.2-0.30, the transference number increases withincreasing salt concentration, indicating a fundamental change in theNa⁺ ion transport mechanism. A similar trend for lithium ions was alsoobserved.

When Na⁺ ions travel in a low salt concentration electrolyte (e.g.x<0.2), a Na⁺ ion can drag multiple solvating molecules along with it.The coordinated migration of such a cluster of charged species can befurther impeded if the fluid viscosity is increased due to more salt andpolymer dissolved in the solvent. In contrast, when an ultra-highconcentration of sodium salt with x>0.2 is present, Na⁺ ions couldsignificantly out-number the available solvating molecules thatotherwise could cluster the sodium ions, forming multi-ion complexspecies and slowing down their diffusion process. This high Na⁺ ionconcentration makes it possible to have more “free Na⁺ ions”(non-clustered), thereby providing a higher Na⁺ transference number(hence, a facile Na⁺ transport). The sodium ion transport mechanismchanges from a multi-ion complex-dominating one (with an overall largerhydrodynamic radius) to single ion-dominating one (with a smallerhydrodynamic radius) having a large number of available free Na⁺ ions.This observation has further asserted that an adequate number of Na⁺ions can quickly move through or from the quasi-solid electrolytes tomake themselves readily available to interact or react with a cathode(during discharge) or an anode (during charge), thereby ensuring a goodrate capability of a sodium secondary cell. Most significantly, thesehighly concentrated electrolytes are non-flammable and safe. Combinedsafety, facile sodium ion transport, and electrochemical performancecharacteristics have been thus far difficult to come by for all types ofsodium and lithium secondary batteries.

Example 8: Lithium Iron Phosphate (LFP) Cathode of a Lithium MetalBattery

LFP powder, un-coated or carbon-coated, is commercially available fromseveral sources. In this example, graphene sheets (RGO) and carbonnano-fiber (CNF) were separately included as conductive filaments in anelectrode containing LFP particles as a cathode active material and anelectrolyte (containing lithium salt and a polymer dissolved in anorganic solvent). The lithium salt used in this example includes lithiumborofluoride (LiBF₄), and the organic solvents are PC, DOL, DEC, andtheir mixtures. A wide range of conducting filament volume fractionsfrom 0.1% to 30% was included in this study. The formation of electrodelayers was accomplished by using the following sequences of steps:

Sequence 1 (S1):

LiBF₄ salt and PEO were dissolved in a mixture of PC and DOL first toform an electrolyte having a combined salt/polymer concentration of 1.0M, 2.5 M, and 3.5 M, respectively. (With a concentration of 2.3 M orhigher, the resulting electrolyte was no longer a liquid electrolyte. Itactually behaves more like a solid and, hence, the term “quasi-solid”.)Then, RGO or CNT filaments were dispersed in the electrolyte to form afilament-electrolyte suspension. Mechanical shearing was used to helpforming uniform dispersion. (This filament-electrolyte suspension, evenwith a low salt concentration of 1.0 M, was also quite viscous). LFPparticles, the cathode active material, were then dispersed in thefilament-electrolyte suspension to form a quasi-solid polymer electrodematerial.

Sequence 2 (S2):

LiBF₄ salt and PEO were dissolved in a mixture of PC and DOL first toform an electrolyte having a combined salt/polymer concentration of 1.0M, 2.5 M, and 3.5 M, respectively. Then, LFP particles, the cathodeactive material, were dispersed in the electrolyte to form an activeparticle-electrolyte suspension. Mechanical shearing was used to helpforming uniform dispersion. (This active particle-electrolytesuspension, even with a low salt concentration of 1.0 M, was also quiteviscous). RGO or CNT filaments were then dispersed in the activeparticle-electrolyte suspension to form a quasi-solid polymer electrodematerial.

Sequence 3 (S3):

First, a desired amount of RGO or CNT filaments was dispersed in theliquid solvent mixture (PC+DOL) containing no lithium salt or polymerdissolved therein. Mechanical shearing was used to help forming uniformsuspension of conducting filaments in the solvent. The LiBF₄ salt, PEO,and LFP particles were then added into the suspension, allowing LiBF₄salt and PEO to get dissolved in the solvent mixture of the suspensionto form an electrolyte having a combined salt/polymer concentration of1.0 M, 2.5 M, and 3.5 M, respectively. Concurrently or subsequently, LFPparticles were dispersed in the electrolyte to form a deformablequasi-solid electrode material, which is composed of active materialparticles and conducting filaments dispersed in a quasi-solid polymerelectrolyte (not a liquid electrolyte and not a solid electrolyte). Inthis quasi-solid electrode material, the conducting filaments percolateto form a 3D network of electron-conducting pathways. This 3D conductingnetwork is maintained when the electrode material is shaped into anelectrode of a battery.

The electrical conductivity of the electrode was measured using afour-point probe method. The results are summarized in FIG. 5(A) andFIG. 5(B). These data indicate that typically percolation of conductivefilaments (CNFs or RGO) to form a 3D network of electron-conductingpaths does not occur until the volume fraction of the conductivefilaments exceeds 10-12%, except for those electrodes made by followingSequence 3 (S3). In other words, the step of dispersing conductivefilaments in a liquid solvent must be conducted before the lithium salt,sodium salt, or the ion-conducting polymer is dissolved in the liquidsolvent and before active material particles are dispersed in thesolvent. Such a sequence also enables the percolation threshold to be aslow as 0.3%-2.0%, making it possible to produce a conductive electrodeby using a minimal amount of conductive additive and, hence, a higherproportion of active material (and higher energy density). Theseobservations were also found to be true of all types of the electrodescontaining active material particles, conductive filaments, andelectrolytes thus far investigated. This is a critically important andunexpected process requirement for the preparation of high-performingalkali metal batteries having both high energy density and high powerdensity.

A quasi-solid cathode, a porous separator, and a quasi-solid anode(prepared in a similar manner, but having artificial graphite particlesas the anode active material) were then assembled together to form aunit cell, which was then encased in a protective housing (a laminatedaluminum-plastic pouch), having two terminals protruding out, to make abattery. Batteries containing a liquid or polymer gel electrolyte (1 M)and quasi-solid polymer electrolytes (2.5 M and 3.5 M) were fabricatedand tested.

For comparison purposes, slurry coating and drying procedures wereconducted to produce conventional electrodes. One anode and one cathode,and a separator disposed between the two electrodes, were then assembledand encased in an Al-plastic laminated packaging envelop, followed byliquid electrolyte injection to form a prior art lithium battery cell.Battery testing results are summarized in Example 19.

Example 9: V₂O₅ as an Example of a Transition Metal Oxide Cathode ActiveMaterial of a Lithium Battery

V₂O₅ powder alone is commercially available. For the preparation of agraphene-supported V₂O₅ powder sample, in a typical experiment, vanadiumpentoxide gels were obtained by mixing V₂O₅ in a LiCl aqueous solution.The Li⁺-exchanged gels obtained by interaction with LiCl solution (theLi:V molar ratio was kept as 1:1) was mixed with a GO suspension andthen placed in a Teflon-lined stainless steel 35 ml autoclave, sealed,and heated up to 180° C. for 12 h. After such a hydrothermal treatment,the green solids were collected, thoroughly washed, ultrasonicated for 2minutes, and dried at 70° C. for 12 h followed by mixing with another0.1% GO in water, ultrasonicating to break down nano-belt sizes, andthen spray-drying at 200° C. to obtain graphene-embraced compositeparticulates.

Both V₂O₅ powder and graphene-supported V₂O₅ powder, separately, alongwith a conductive additive (CNTs), and a liquid electrolyte, were thenincorporated in a battery using both the presently invented method andthe conventional procedure of slurry coating, drying and layerlaminating.

Example 10: LiCoO₂ as an Example of Lithium Transition Metal OxideCathode Active Material for a Lithium-Ion Battery

Commercially available LiCoO₂ powder and multi-walled carbon nanotubes(MW-CNTs) were dispersed in a quasi-solid polymer electrolyte to form aquasi-solid electrode. Two types of quasi-solid anode were prepared tocouple with the cathode. One includes graphite particles as the anodeactive material and the other graphene-embraced Si nano particles as theanode active material. The electrolyte solvent used was EC-VC (80/20ratio) and LiBOB+PEO were dissolved in this organic solvent to form thequasi-solid polymer electrolyte. Each cell contains a quasi-solid anode,a separator layer, and a quasi-solid cathode assembled together and thenhermetically sealed.

On a separate basis, LiCoO₂ powder, MW-CNTs, and PVDF resin binder weredispersed in NMP solvent to form a slurry, which was coated onto bothsides of a AL foil current collector and then dried under vacuum to forma cathode layer. Graphite particles and PVDF resin binder were dispersedin NMP solvent to form a slurry, which was coated onto both sides of aCu foil current collector and then dried under vacuum to form an anodelayer. The anode layer, separator, cathode layer were then laminated andencased in an Al-plastic housing, which was injected with a liquidelectrolyte to form a conventional lithium-ion battery.

Example 11: Organic Material (Li₂C₆O₆) as a Cathode Active Material of aLithium Metal Battery

In order to synthesize dilithium rhodizonate (Li₂C₆O₆), the rhodizonicacid dihydrate (species 1 in the following scheme) was used as aprecursor. A basic lithium salt, Li₂CO₃ can be used in aqueous media toneutralize both enediolic acid functions. Strictly stoichiometricquantities of both reactants, rhodizonic acid and lithium carbonate,were allowed to react for 10 hours to achieve a yield of 90%. Dilithiumrhodizonate (species 2) was readily soluble even in a small amount ofwater, implying that water molecules are present in species 2. Water wasremoved in a vacuum at 180° C. for 3 hours to obtain the anhydrousversion (species 3).

A mixture of a cathode active material (Li₂C₆O₆) and a conductiveadditive (carbon black, 15%) was ball-milled for 10 minutes and theresulting blend was grinded to produce composite particles. Theelectrolyte was 2.5 M of lithium hexafluorophosphate (LiPF₆) and PPO inPC-EC.

It may be noted that the two Li atoms in the formula Li₂C₆O₆ are part ofthe fixed structure and they do not participate in reversible lithiumion storing and releasing. This implies that lithium ions must come fromthe anode side. Hence, there must be a lithium source (e.g. lithiummetal or lithium metal alloy) at the anode. As illustrated in FIG. 1(D),the anode current collector (Cu foil) is deposited with a layer oflithium (e.g. via sputtering or electrochemical plating, or by using alithium foil). This was followed by assembling the lithium-coated layer,a porous separator, and a quasi-solid cathode into a cell. The cathodeactive material and conductive additive (Li₂C₆O₆/C composite particles+CNFs) were dispersed in the liquid electrolyte. For comparison, thecorresponding conventional Li metal cell was also fabricated by theconventional procedures of slurry coating, drying, laminating,packaging, and electrolyte injection.

Example 12: Metal Naphthalocyanine-RGO Hybrid Cathode of a Lithium MetalBattery

Copper naphthalocyanine (CuPc)-coated graphene sheets were obtained byvaporizing CuPc in a chamber along with a graphene film (5 nm) preparedfrom spin coating of RGO-water suspension. The resulting coated film wascut and milled to produce CuPc-coated graphene sheets, which were usedas a cathode active material in a lithium metal battery having a lithiummetal foil as the anode active material and 1.0 M and 3.0 M of LiClO₄and PEO in propylene carbonate (PC) solution as the electrolyte.

Example 13: Preparation of MoS₂/RGO Hybrid Material as a Cathode ActiveMaterial of a Lithium Metal Battery

A wide variety of inorganic materials were investigated in this example.For instance, an ultra-thin MoS₂/RGO hybrid was synthesized by aone-step solvothermal reaction of (NH₄)₂MoS₄ and hydrazine in anN,N-dimethylformamide (DMF) solution of oxidized graphene oxide (GO) at200° C. In a typical procedure, 22 mg of (NH₄)₂MoS₄ was added to 10 mgof GO dispersed in 10 ml of DMF. The mixture was sonicated at roomtemperature for approximately 10 min until a clear and homogeneoussolution was obtained. After that, 0.1 ml of N₂H₄.H₂O was added. Thereaction solution was further sonicated for 30 min before beingtransferred to a 40 mL Teflon-lined autoclave. The system was heated inan oven at 200° C. for 10 h. Product was collected by centrifugation at8000 rpm for 5 min, washed with DI water and recollected bycentrifugation. The washing step was repeated for at least 5 times toensure that most DMF was removed. Finally, the dried product was mixedwith some carbon fibers and a quasi-solid polymer (PAN) electrolyte toform a deformable quasi-solid cathode.

Example 14: Preparation of Two-Dimensional (2D) Layered Bi₂Se₃Chalcogenide Nanoribbons

The preparation of (2D) layered Bi₂Se₃ chalcogenide nanoribbons iswell-known in the art. For instance, Bi₂Se₃ nanoribbons were grown usingthe vapor-liquid-solid (VLS) method. Nanoribbons herein produced are, onaverage, 30-55 nm thick with widths and lengths ranging from hundreds ofnanometers to several micrometers. Larger nanoribbons were subjected toball-milling for reducing the lateral dimensions (length and width) tobelow 200 nm. Nanoribbons prepared by these procedures and eithergraphene sheets or exfoliated graphite flakes were combined with aquasi-solid polymer electrolyte to form a deformable cathode of alithium metal battery.

Example 15: MXenes Powder+Chemically Activated RGO

Selected MXenes, were produced by partially etching out certain elementsfrom layered structures of metal carbides such as Ti₃AlC₂. For instance,an aqueous 1 M NH₄HF₂ was used at room temperature as the etchant forTi₃AlC₂. Typically, MXene surfaces are terminated by O, OH, and/or Fgroups, which is why they are usually referred to as M_(n+1)X_(n)T_(x),where M is an early transition metal, X is C and/or N, T representsterminating groups (O, OH, and/or F), n=1, 2, or 3, and x is the numberof terminating groups. The MXene materials investigated includeTi₂CT_(x), Nb₂CT_(x), V₂CT_(x), Ti₃CNT_(x), and Ta₄C₃T_(x). Typically,2-35% graphene sheets were mixed in a solvent, followed by adding 35-95%MXene, some Li/Na salt, and a polymer to form a quasi-solidelectrolyte-based cathode that is deformable, conformable, andconductive.

Example 16: Preparation of Graphene-Supported MnO₂ Cathode ActiveMaterial

The MnO₂ powder was synthesized by two methods (each with or without thepresence of graphene sheets). In one method, a 0.1 mol/L KMnO₄ aqueoussolution was prepared by dissolving potassium permanganate in deionizedwater. Meanwhile 13.32 g surfactant of high purity sodiumbis(2-ethylhexyl) sulfosuccinate was added in 300 mL iso-octane (oil)and stirred well to get an optically transparent solution. Then, 32.4 mLof 0.1 mol/L KMnO₄ solution and selected amounts of GO solution wereadded in the solution, which was ultrasonicated for 30 min to prepare adark brown precipitate. The product was separated, washed several timeswith distilled water and ethanol, and dried at 80° C. for 12 h. Thesample is graphene-supported MnO₂ in a powder form, which, along with alithium salt and PEO, was dispersed in a CNT-containing electrolyte toform a quasi-solid polymer electrolyte-based cathode electrode.

Example 17: Graphene-Enhanced Nano Silicon as an Anode Active Materialof a Lithium-Ion Battery

Graphene-wrapped Si particles were available from Angstron Energy Co.,Dayton, Ohio). Quasi-solid anode electrodes were prepared by dispersingpristine graphene sheets (as conductive filaments) in a PC-DOL (50/50ratio) mixture, followed by dispersing graphene-wrapped Si particles(anode active material), and by dissolving 3.5 M of lithiumhexafluorophosphate (LiPF₆) in the mixture solvent at 60° C. Then, DOLwas removed to obtain a quasi-solid electrolyte containing about 5.0 Mof LiPF₆ in PC. This brings LiPF₆ in a supersaturated state since themaximum solubility of LiPF₆ in PC is known to be lower than 3.0 M atroom temperature.

Example 18: Cobalt Oxide (Co₃O₄) Particulates as an Anode ActiveMaterial

Although LiCoO₂ is a cathode active material, Co₃O₄ is an anode activematerial of a lithium-ion battery since LiCoO₂ is at an electrochemicalpotential of approximately +4.0 volts relative to Li/Li⁺ and Co₃O₄ is atan electrochemical potential of approximately +0.8 volts relative toLi/Li⁺.

An appropriate amount of inorganic salts Co(NO₃)₂.6H₂O and,subsequently, ammonia solution (NH₃.H₂O, 25 wt %) were slowly added intoa GO suspension. The resulting precursor suspension was stirred forseveral hours under an argon flow to ensure a complete reaction. Theobtained Co(OH)₂/graphene precursor suspension was filtered and driedunder vacuum at 70° C. to obtain a Co(OH)₂/graphene composite precursor.This precursor was calcined at 450° C. in air for 2 h to formCo₃O₄/graphene composites, which were mixed into a quasi-solid polymerelectrolyte to prepare a quasi-solid electrode.

Example 19: Graphene-Enhanced Tin Oxide Particulates as an Anode ActiveMaterial

Tin oxide (SnO₂) nano particles were obtained by the controlledhydrolysis of SnCl₄.5H₂O with NaOH using the following procedure:SnCl₄.5H₂O (0.95 g, 2.7 m-mol) and NaOH (0.212 g, 5.3 m-mol) weredissolved in 50 mL of distilled water each. The NaOH solution was addeddrop-wise under vigorous stirring to the tin chloride solution at a rateof 1 mL/min. This solution was homogenized by sonication for 5 min.Subsequently, the resulting hydrosol was reacted with the GO dispersionfor 3 hours. To this mixed solution, few drops of 0.1 M of H₂SO₄ wereadded to flocculate the product. The precipitated solid was collected bycentrifugation, washed with water and ethanol, and dried in vacuum. Thedried product was heat-treated at 400° C. for 2 h under Ar atmosphereand was used as an anode active material.

Example 20: Preparation and Electrochemical Testing of Various BatteryCells

For most of the anode and cathode active materials investigated, weprepared lithium-ion cells or lithium metal cells using both thepresently invented method and the conventional method.

With the conventional method, a typical anode composition includes 85wt. % active material (e.g., Si- or Co₃O₄-coated graphene sheets), 7 wt.% acetylene black (Super-P), and 8 wt. % polyvinylidene fluoride binder(PVDF, 5 wt. % solid content) dissolved in N-methyl-2-pyrrolidinoe(NMP). After coating the slurries on Cu foil, the electrodes were driedat 120° C. in vacuum for 2 h to remove the solvent. With the instantmethod, typically no binder resin is needed or used, saving 8% weight(reduced amount of non-active materials). Cathode layers are made in asimilar manner (using Al foil as the cathode current collector) usingthe conventional slurry coating and drying procedures. An anode layer,separator layer (e.g. Celgard 2400 membrane), and a cathode layer arethen laminated together and housed in a plastic-Al envelop. As anexample, the cell is then injected with 1M LiPF₆ electrolyte solutiondissolved in a mixture of ethylene carbonate (EC) and diethyl carbonate(DEC) (EC-DEC, 1:1 v/v). In some cells, ionic liquids were used as theliquid electrolyte. The cell assemblies were made in an argon-filledglove-box.

In the presently invented process, preferably a quasi-solid anode, aporous separator, and a quasi-solid cathode are assembled in aprotective housing. The pouch was then sealed.

The cyclic voltammetry (CV) measurements were carried out using an Arbinelectrochemical workstation at a typical scanning rate of 1 mV/s. Inaddition, the electrochemical performances of various cells were alsoevaluated by galvanostatic charge/discharge cycling at a current densityof from 50 mA/g to 10 A/g. For long-term cycling tests, multi-channelbattery testers manufactured by LAND were used.

Example 21: Representative Testing Results

For each sample, several current densities (representingcharge/discharge rates) were imposed to determine the electrochemicalresponses, allowing for calculations of energy density and power densityvalues required of the construction of a Ragone plot (power density vs.energy density). Shown in FIG. 6 are Ragone plots (gravimetric powerdensity vs. energy density) of lithium-ion battery cells containinggraphite particles as the anode active material and carbon-coated LFPparticles as the cathode active materials. Three of the 4 data curvesare for the cells prepared according to an embodiment of instantinvention (with Sequence S1, S2, and S3, respectively) and the remainingone by the conventional slurry coating of electrodes (roll-coating).Several significant observations can be made from these data:

The gravimetric energy densities and power densities of the lithium-ionbattery cells prepared by the presently invented method aresignificantly higher than those of their counterparts prepared via theconventional roll-coating method (denoted as “conventional”). A changefrom an anode thickness of 160 μm (coated on a flat solid Cu foil) to athickness of 420 μm and a corresponding change in the cathode tomaintain a balanced capacity ratio results in a gravimetric energydensity increase from 161 Wh/kg to 226 Wh/kg (S1), 227 Wh/kg (S2), and264 Wh/kg (S3), respectively. Also surprisingly, the battery containingpresently invented quasi-solid electrodes having a 3D network ofelectron-conducting pathways (due to percolation of conductivefilaments) deliver a significantly higher energy density and higherpower density.

These huge differences cannot be simply ascribed to the increases in theelectrode thickness and the mass loading. The differences are likely dueto the significantly higher active material mass loading (not just massloading) and the higher conductivity associated with the presentlyinvented cells, reduced proportion of overhead (non-active) componentsrelative to the active material weight/volume, and surprisingly betterutilization of the electrode active material (most, if not all, of thegraphite particles and LFP particles contributing to the lithium ionstorage capacity due to higher conductivity and no dry pockets orineffective spots in the electrode, particularly under highcharge/discharge rate conditions).

FIG. 7 shows the Ragone plots (gravimetric power density vs. gravimetricenergy density) of two cells, both containing graphene-embraced Si nanoparticles as the anode active material and LiCoO₂ nano particles as thecathode active material. The experimental data were obtained from theLi-ion battery cells that were prepared by the presently invented methodand those by the conventional slurry coating of electrodes.

These data indicate that the gravimetric energy densities and powerdensities of the battery cells prepared by the presently invented methodare significantly higher than those of their counterparts prepared viathe conventional method. Again, the differences are huge. Theconventionally made cells exhibit a gravimetric energy density of 265Wh/kg, but the presently invented cells deliver an energy density of 382Wh/kg (S1) and 420 Wh/kg (S3), respectively. The power densities as highas 1425 W/kg and 1,650 W/kg are also unprecedented for lithium-ionbatteries.

These energy density and power density differences are mainly due to thehigh active material mass loading (>25 mg/cm² in the anode and >45mg/cm² in the cathode) and high electrode conductivity associated withthe presently invented cells, reduced proportion of overhead(non-active) components relative to the active material weight/volume,and the ability of the inventive method to better utilize the activematerial particles (all particles being accessible to liquid electrolyteand fast ion and electron kinetics).

Shown in FIG. 8 are Ragone plots of lithium metal batteries containing alithium foil as the anode active material, dilithium rhodizonate(Li₂C₆O₆) as the cathode active material, and lithium salt(LiPF₆)-PC/DEC as organic electrolyte (both 1.5 M and 5.0 M). Thequasi-solid electrodes were prepared according to the sequences S2 andS3 as described in Example 8. The data are for the three lithium metalcells prepared by the presently invented method and those by theconventional slurry coating of electrodes.

These data indicate that the gravimetric energy densities and powerdensities of the lithium metal cells prepared by the presently inventedmethod are significantly higher than those of their counterpartsprepared via the conventional method. Again, the differences are hugeand are likely due to the significantly higher active material massloading (not just mass loading) and higher conductivity associated withthe presently invented electrodes, reduced proportion of overhead(non-active) components relative to the active material weight/volume,and surprisingly better utilization of the electrode active material(most, if not all, of the active material contributing to the lithiumion storage capacity due to higher conductivity and no dry pockets orineffective spots in the electrode, particularly under highcharge/discharge rate conditions).

Quite noteworthy and unexpected is the observation that the gravimetricenergy density of the presently invented lithium metal-organic cathodecell is as high as 502 Wh/kg, higher than those of all rechargeablelithium-metal or lithium-ion batteries ever reported (recall thatcurrent Li-ion batteries store 150-220 Wh/kg based on the total cellweight). Furthermore, for organic cathode active material-based lithiumbatteries, a gravimetric power density of 1,578 W/kg and would have beenun-thinkable. The cells containing a quasi-solid electrode preparedaccording to Sequence 3 exhibit significantly higher energy densitiesand power densities as compared to those of the conventional sequenceS2. Also, higher concentration electrolytes (quasi-solid electrolytes)are surprisingly more conducive to achieving higher energy densities andpower densities.

The above performance features of lithium batteries are also observedwith corresponding sodium batteries. Due to page limitation, the datafor sodium batteries will not be presented here. However, as an example,FIG. 9 indicates Ragone plots of two sodium-ion capacitors eachcontaining pre-sodiated hard carbon particles as the anode activematerial and graphene sheets as a cathode active material; one cellhaving an anode prepared by the conventional slurry coating process andthe other cell having a quasi-solid anode prepared according to apresently invented method. Again, the quasi-solid electrode-based celldelivers significantly higher energy density and higher power density.Lithium-ion capacitors were found to follow similar trend.

It is of significance to point out that reporting the energy and powerdensities per weight of active material alone on a Ragone plot, as didby many researchers, may not give a realistic picture of the performanceof the assembled supercapacitor cell. The weights of other devicecomponents also must be taken into account. These overhead components,including current collectors, electrolyte, separator, binder,connectors, and packaging, are non-active materials and do notcontribute to the charge storage amounts. They only add weights andvolumes to the device. Hence, it is desirable to reduce the relativeproportion of overhead component weights and increase the activematerial proportion. However, it has not been possible to achieve thisobjective using conventional battery production processes. The presentinvention overcomes this long-standing, most serious problem in the artof lithium batteries.

In a commercial lithium-ion batteries having an electrode thickness of100-200 μm, the weight proportion of the anode active material (e.g.graphite or carbon) in a lithium-ion battery is typically from 12% to17%, and that of the cathode active material (for inorganic material,such as LiMn₂O₄) from 22% to 41%, or from 10% to 15% for organic orpolymeric. Hence, a factor of 3 to 4 is frequently used to extrapolatethe energy or power densities of the device (cell) from the propertiesbased on the active material weight alone. In most of the scientificpapers, the properties reported are typically based on the activematerial weight alone and the electrodes are typically very thin (<<100μm, and mostly <<50 μm). The active material weight is typically from 5%to 10% of the total device weight, which implies that the actual cell(device) energy or power densities may be obtained by dividing thecorresponding active material weight-based values by a factor of 10 to20. After this factor is taken into account, the properties reported inthese papers do not really look any better than those of commercialbatteries. Thus, one must be very careful when it comes to read andinterpret the performance data of batteries reported in the scientificpapers and patent applications.

We claim:
 1. An alkali metal cell comprising: (a) a quasi-solid cathodecontaining about 30% to about 94.99% by volume of a cathode activematerial, about 5% to about 40% by volume of a first electrolytecontaining an alkali salt and an ion-conducting polymer dissolved ordispersed in a solvent, and about 0.01% to about 30% by volume of aconductive additive wherein said conductive additive, containingconductive filaments, forms a 3D network of electron-conducting pathwayssuch that the quasi-solid cathode has an electrical conductivity fromabout 10⁻⁶ S/cm to about 300 S/cm, wherein said cathode active materialconstitutes an electrode active material mass loading no less than 10mg/cm², wherein said ion-conducting polymer is selected frompolypropylene oxide (PPO), poly(acrylonitrile) (PAN), poly(methylmethacrylate) (PMMA), poly(vinylidene fluoride) (PVdF), poly bis-methoxyethoxyethoxide-phosphazenex, polyvinyl chloride, polydimethylsiloxane,poly(vinylidene fluoride)-hexafluoropropylene (PVDF-HFP), a sulfonatedderivative thereof, a sulfonated polymer, or a combination thereof; (b)an anode; and (c) an ion-conducting membrane or porous separatordisposed between the anode and the quasi-solid cathode; wherein thequasi-solid cathode has a thickness no less than 200 μm.
 2. The alkalimetal cell of claim 1, wherein said anode contains a quasi-solid anodecontaining about 30% to about 94.99% by volume of an anode activematerial, about 5% to about 40% by volume of a second electrolytecontaining an alkali salt and an ion-conducting polymer dissolved ordispersed in a solvent, and about 0.01% to about 30% by volume of aconductive additive wherein said conductive additive, containingconductive filaments, forms a 3D network of electron-conducting pathwayssuch that the quasi-solid anode has an electrical conductivity fromabout 10⁻⁶ S/cm to about 300 S/cm; wherein said quasi-solid anode has athickness no less than 200 μm.
 3. An alkali metal cell comprising: A) aquasi-solid anode containing about 30% to about 94.99% by volume of ananode active material, about 5% to about 40% by volume of an electrolytecontaining an alkali salt and an ion-conducting polymer dissolved ordispersed in a solvent, and about 0.01% to about 30% by volume of aconductive additive wherein said conductive additive, containingconductive filaments, forms a 3D network of electron-conducting pathwayssuch that the quasi-solid anode has an electrical conductivity fromabout 10⁻⁶ S/cm to about 300 S/cm, wherein said anode active materialconstitutes an electrode active material mass loading no less than 10mg/cm², wherein said ion-conducting polymer is selected frompolypropylene oxide (PPO), poly(acrylonitrile) (PAN), poly(methylmethacrylate) (PMMA), poly(vinylidene fluoride) (PVdF), poly bis-methoxyethoxyethoxide-phosphazenex, polyvinyl chloride, polydimethylsiloxane,poly(vinylidene fluoride)-hexafluoropropylene (PVDF-HFP), a sulfonatedderivative thereof, a sulfonated polymer, or a combination thereof; B) acathode; and C) an ion-conducting membrane or porous separator disposedbetween the quasi-solid anode and the cathode; wherein said quasi-solidanode has a thickness no less than 200 μm.
 4. The alkali metal cell ofclaim 2, wherein said second electrolyte contains a quasi-solid polymerelectrolyte containing an ion-conducting polymer selected frompoly(ethylene oxide) (PEO) having a molecular weight lower than 1×10⁶g/mole, polypropylene oxide (PPO), poly(acrylonitrile) (PAN),poly(methyl methacrylate) (PMMA), poly(vinylidene fluoride) (PVdF), polybis-methoxy ethoxyethoxide-phosphazenex, polyvinyl chloride,polydimethylsiloxane, poly(vinylidene fluoride)-hexafluoropropylene(PVDF-HFP), a sulfonated derivative thereof, a sulfonated polymer, or acombination thereof.
 5. An alkali metal cell comprising: (A) aquasi-solid cathode containing about 30% to about 94.99% by volume of acathode active material, about 5% to about 40% by volume of a firstelectrolyte containing an alkali salt and an ion-conducting polymerdissolved or dispersed in a solvent, and about 0.01% to about 30% byvolume of a conductive additive wherein said conductive additive,containing conductive filaments, forms a 3D network ofelectron-conducting pathways such that the quasi-solid cathode has anelectrical conductivity from about 10⁻⁶ S/cm to about 300 S/cm, whereinsaid cathode active material constitutes an electrode active materialmass loading no less than 10 mg/cm², wherein said ion-conducting polymeris selected from the group consisting of poly(perfluoro sulfonic acid),sulfonated polytetrafluoroethylene, sulfonated perfluoroalkoxyderivatives of polytetrafluoroethylene, sulfonated polysulfone,sulfonated poly(ether ketone), sulfonated poly (ether ether ketone),sulfonated polystyrene, sulfonated polyimide, sulfonatedstyrene-butadiene copolymers, sulfonated poly chloro-trifluoroethylene(PCTFE), sulfonated perfluoroethylene-propylene copolymer (FEP),sulfonated ethylene-chlorotrifluoroethylene copolymer (ECTFE),sulfonated polyvinylidenefluoride (PVDF), sulfonated copolymers ofpolyvinylidenefluoride with hexafluoropropene and tetrafluoroethylene,sulfonated copolymers of ethylene and tetrafluoroethylene (ETFE),sulfonated polybenzimidazole (PBI), their chemical derivatives,copolymers, blends and combinations thereof; (B) an anode; and (C) anion-conducting membrane or porous separator disposed between the anodeand the quasi-solid cathode; wherein the quasi-solid cathode has athickness no less than 200 μm.
 6. The alkali metal cell of claim 2,wherein said ion-conducting polymer is selected from the groupconsisting of poly(perfluoro sulfonic acid), sulfonatedpolytetrafluoroethylene, sulfonated perfluoroalkoxy derivatives ofpolytetrafluoroethylene, sulfonated polysulfone, sulfonated poly(etherketone), sulfonated poly (ether ether ketone), sulfonated polystyrene,sulfonated polyimide, sulfonated styrene-butadiene copolymers,sulfonated poly chloro-trifluoroethylene (PCTFE), sulfonatedperfluoroethylene-propylene copolymer (FEP), sulfonatedethylene-chlorotrifluoroethylene copolymer (ECTFE), sulfonatedpolyvinylidenefluoride (PVDF), sulfonated copolymers ofpolyvinylidenefluoride with hexafluoropropene and tetrafluoroethylene,sulfonated copolymers of ethylene and tetrafluoroethylene (ETFE),sulfonated polybenzimidazole (PBI), their chemical derivatives,copolymers, blends and combinations thereof.
 7. An alkali metal cellcomprising: (A) a quasi-solid anode containing about 30% to about 94.99%by volume of an anode active material, about 5% to about 40% by volumeof an electrolyte containing an alkali salt and an ion-conductingpolymer dissolved or dispersed in a solvent, and about 0.01% to about30% by volume of a conductive additive wherein said conductive additive,containing conductive filaments, forms a 3D network ofelectron-conducting pathways such that the quasi-solid anode has anelectrical conductivity from about 10⁻⁶ S/cm to about 300 S/cm, whereinsaid anode active material constitutes an electrode active material massloading no less than 10 mg/cm², wherein said ion-conducting polymer isselected from the group consisting of poly(perfluoro sulfonic acid),sulfonated polytetrafluoroethylene, sulfonated perfluoroalkoxyderivatives of polytetrafluoroethylene, sulfonated polysulfone,sulfonated poly(ether ketone), sulfonated poly (ether ether ketone),sulfonated polystyrene, sulfonated polyimide, sulfonatedstyrene-butadiene copolymers, sulfonated poly chloro-trifluoroethylene(PCTFE), sulfonated perfluoroethylene-propylene copolymer (FEP),sulfonated ethylene-chlorotrifluoroethylene copolymer (ECTFE),sulfonated polyvinylidenefluoride (PVDF), sulfonated copolymers ofpolyvinylidenefluoride with hexafluoropropene and tetrafluoroethylene,sulfonated copolymers of ethylene and tetrafluoroethylene (ETFE),sulfonated polybenzimidazole (PBI), their chemical derivatives,copolymers, blends and combinations thereof; (B) a cathode; and (C) anion-conducting membrane or porous separator disposed between thequasi-solid anode and the cathode; wherein said quasi-solid anode has athickness no less than 200 μm.
 8. The alkali metal cell of claim 1,wherein said conductive filaments are selected from carbon fibers,graphite fibers, carbon nano-fibers, graphite nano-fibers, carbonnanotubes, needle coke, carbon whiskers, conductive polymer fibers,conductive material-coated fibers, metal nano-wires, metal fibers, metalwires, graphene sheets, expanded graphite platelets, a combinationthereof, or a combination thereof with non-filamentary conductiveparticles.
 9. The alkali metal cell of claim 1, wherein saidion-conducting polymer does not form a matrix in said quasi-solidcathode.
 10. The alkali metal cell of claim 3, wherein saidion-conducting polymer does not form a matrix in said quasi-solid anode.11. The alkali metal cell of claim 1, wherein said quasi-solid cathodemaintains an electrical conductivity from about 10⁻³ S/cm to about 10S/cm.
 12. The alkali metal cell of claim 1, wherein said conductivefilaments are bonded together by a resin at points of intersectionbetween the conductive filaments.
 13. The alkali metal cell of claim 1,wherein said quasi-solid cathode contains about 0.1% to about 20% byvolume of a conductive additive.
 14. The alkali metal cell of claim 1,wherein said quasi-solid cathode contains about 1% to about 10% byvolume of a conductive additive.
 15. The alkali metal cell of claim 1,wherein the quantity of the active material is about 40% to about 90% byvolume of the cathode active material.
 16. The alkali metal cell ofclaim 1, wherein the quantity of the active material is about 50% toabout 85% by volume of the cathode active material.
 17. The alkali metalcell of claim 1, wherein said first electrolyte is in a supersaturatedstate.
 18. The alkali metal cell of claim 2, wherein said firstelectrolyte or second electrolyte is in a supersaturated state.
 19. Thealkali metal cell of claim 1, wherein said solvent is selected fromwater, an organic solvent, an ionic liquid, or a mixture of an organicsolvent and an ionic liquid.
 20. The alkali metal cell of claim 2,wherein said first electrolyte or second electrolyte contains a solventselected from water, an organic solvent, an ionic liquid, or a mixtureof an organic solvent and an ionic liquid.
 21. The alkali metal cell ofclaim 2, wherein said alkali metal cell is a lithium metal cell,lithium-ion cell, or lithium-ion capacitor cell and said anode activematerial is selected from the group consisting of: (a) Particles oflithium metal or a lithium metal alloy; (b) Natural graphite particles,artificial graphite particles, meso-carbon microbeads (MCMB), carbonparticles, needle coke, carbon nanotubes, carbon nano-fibers, carbonfibers, and graphite fibers; (c) Silicon (Si), germanium (Ge), tin (Sn),lead (Pb), antimony (Sb), bismuth (Bi), zinc (Zn), aluminum (Al), nickel(Ni), cobalt (Co), manganese (Mn), titanium (Ti), iron (Fe), and cadmium(Cd); (d) Alloys or intermetallic compounds of Si, Ge, Sn, Pb, Sb, Bi,Zn, Al, or Cd with other elements, wherein said alloys or compounds arestoichiometric or non-stoichiometric; (e) Oxides, carbides, nitrides,sulfides, phosphides, selenides, and tellurides of Si, Ge, Sn, Pb, Sb,Bi, Zn, Al, Fe, Ni, Co, Ti, Mn, or Cd, and their mixtures or composites;(f) Pre-lithiated versions thereof; (g) Pre-lithiated graphene sheets;and combinations thereof.
 22. The alkali metal cell of claim 21, whereinsaid pre-lithiated graphene sheets are selected from pre-lithiatedversions of pristine graphene, graphene oxide, reduced graphene oxide,graphene fluoride, graphene chloride, graphene bromide, graphene iodide,hydrogenated graphene, nitrogenated graphene, boron-doped graphene,nitrogen-doped graphene, chemically functionalized graphene, aphysically or chemically activated or etched version thereof, or acombination thereof.
 23. The alkali metal cell of claim 2, wherein saidalkali metal cell is a sodium metal cell, sodium-ion cell, or sodium-ioncapacitor and said anode active material contains an alkaliintercalation compound selected from petroleum coke, carbon black,amorphous carbon, activated carbon, hard carbon, soft carbon, templatedcarbon, hollow carbon nanowires, hollow carbon sphere, titanates,NaTi₂(PO₄)₃, Na₂Ti₃O₇, Na₂C₈H₄O₄, Na₂TP, Na_(x)TiO₂ (x=0.2 to 1.0),Na₂C₈H₄O₄, carboxylate based materials, C₈H₄Na₂O₄, C₈H₆O₄, C₈H₅NaO₄,C₈Na₂F₄O₄, C₁₀H₂Na₄O₈, C₁₄H₄O₆, C₁₄H₄Na₄O₈, or a combination thereof.24. The alkali metal cell of claim 2, wherein said alkali metal cell isa sodium metal cell, sodium-ion cell, or sodium-ion capacitor and saidanode active material is selected from the group consisting of: a)Particles of sodium metal or a sodium metal alloy; b) Natural graphiteparticles, artificial graphite particles, meso-carbon microbeads (MCMB),carbon particles, needle coke, carbon nanotubes, carbon nano-fibers,carbon fibers, and graphite fibers; c) Sodium-doped silicon (Si),germanium (Ge), tin (Sn), lead (Pb), antimony (Sb), bismuth (Bi), zinc(Zn), aluminum (Al), titanium (Ti), cobalt (Co), nickel (Ni), manganese(Mn), cadmium (Cd), and mixtures thereof; d) Sodium-containing alloys orintermetallic compounds of Si, Ge, Sn, Pb, Sb, Bi, Zn, Al, Ti, Co, Ni,Mn, Cd, and their mixtures; e) Sodium-containing oxides, carbides,nitrides, sulfides, phosphides, selenides, tellurides, or antimonides ofSi, Ge, Sn, Pb, Sb, Bi, Zn, Al, Fe, Ti, Co, Ni, Mn, Cd, and mixtures orcomposites thereof; f) Sodium salts; g) Graphene sheets pre-loaded withsodium ions; and combinations thereof.
 25. The alkali metal cell ofclaim 1, wherein said alkali metal cell is a lithium metal cell orlithium-ion cell and said cathode active material contains a lithiumintercalation compound selected from the group consisting of lithiumcobalt oxide, doped lithium cobalt oxide, lithium nickel oxide, dopedlithium nickel oxide, lithium manganese oxide, doped lithium manganeseoxide, lithium vanadium oxide, doped lithium vanadium oxide, lithiummixed-metal oxides, lithium iron phosphate, lithium vanadium phosphate,lithium manganese phosphate, lithium mixed-metal phosphates, metalsulfides, and combinations thereof.
 26. The alkali metal cell of claim1, wherein said alkali metal cell is a lithium metal cell or lithium-ioncell and said cathode active material contains a lithium intercalationcompound or lithium-absorbing compound selected from an inorganicmaterial, an organic or polymeric material, a metaloxide/phosphate/sulfide, or a combination thereof.
 27. The alkali metalcell of claim 26, wherein said metal oxide/phosphate/sulfide is selectedfrom a lithium cobalt oxide, lithium nickel oxide, lithium manganeseoxide, lithium vanadium oxide, lithium-mixed metal oxide, lithium ironphosphate, lithium manganese phosphate, lithium vanadium phosphate,lithium mixed metal phosphate, transition metal sulfide, or acombination thereof.
 28. The alkali metal cell of claim 26, wherein saidinorganic material is selected from sulfur, sulfur compound, lithiumpolysulfide, transition metal dichalcogenide, a transition metaltrichalcogenide, or a combination thereof.
 29. The alkali metal cell ofclaim 26, wherein said inorganic material is selected from TiS₂, TaS₂,MoS₂, NbSe₃, MnO₂, CoO₂, an iron oxide, a vanadium oxide, or acombination thereof.
 30. The alkali metal cell of claim 26, wherein saidmetal oxide/phosphate/sulfide contains a vanadium oxide selected fromthe group consisting of VO₂, Li_(x)VO₂, V₂O₅, Li_(x)V₂O₅, V₃O₈,Li_(x)V₃O₈, Li_(x)V₃O₇, V₄O₉, Li_(x)V₄O₉, V₆O₁₃, Li_(x)V₆O₁₃, theirdoped versions, their derivatives, and combinations thereof, wherein0.1<x<5.
 31. The alkali metal cell of claim 26, wherein said metaloxide/phosphate/sulfide is selected from a layered compound LiMO₂,spinel compound LiM₂O₄, olivine compound LiMPO₄, silicate compoundLi₂MSiO₄, Tavorite compound LiMPO₄F, borate compound LiMBO₃, or acombination thereof, wherein M is a transition metal or a mixture ofmultiple transition metals.
 32. The alkali metal cell of claim 26,wherein said inorganic material is selected from: (a) bismuth selenideor bismuth telluride, (b) transition metal dichalcogenide ortrichalcogenide, (c) sulfide, selenide, or telluride of niobium,zirconium, molybdenum, hafnium, tantalum, tungsten, titanium, cobalt,manganese, iron, nickel, or a transition metal; (d) boron nitride, or(e) a combination thereof.
 33. The alkali metal cell of claim 26,wherein said organic material or polymeric material is selected fromPoly(anthraquinonyl sulfide) (PAQS), a lithium oxocarbon,3,4,9,10-perylenetetracarboxylic dianhydride (PTCDA),poly(anthraquinonyl sulfide), pyrene-4,5,9,10-tetraone (PYT),polymer-bound PYT, Quino(triazene), redox-active organic material,Tetracyanoquinodimethane (TCNQ), tetracyanoethylene (TCNE),2,3,6,7,10,11-hexamethoxytriphenylene (HMTP), poly(5-amino-1,4-dyhydroxyanthraquinone) (PADAQ), phosphazene disulfide polymer ([(NPS₂)₃] n),lithiated 1,4,5,8-naphthalenetetraol formaldehyde polymer,Hexaazatrinaphtylene (HATN), Hexaazatriphenylene hexacarbonitrile(HAT(CN)₆), 5-Benzylidene hydantoin, Isatine lithium salt, Pyromelliticdiimide lithium salt, tetrahydroxy-p-benzoquinone derivatives (THQLi₄),N,N′-diphenyl-2,3,5,6-tetraketopiperazine (PHP),N,N′-diallyl-2,3,5,6-tetraketopiperazine (AP),N,N′-dipropyl-2,3,5,6-tetraketopiperazine (PRP), a thioether polymer, aquinone compound, 1,4-benzoquinone, 5,7,12,14-pentacenetetrone (PT),5-amino-2,3-dihydro-1,4-dyhydroxy anthraquinone (ADDAQ),5-amino-1,4-dyhydroxy anthraquinone (ADAQ), calixquinone, Li₄C₆O₆,Li₂C₆O₆, Li₆C₆O₆, or a combination thereof.
 34. The alkali metal cell ofclaim 33, wherein said thioether polymer is selected fromPoly[methanetetryl-tetra(thiomethylene)] (PMTTM),Poly(2,4-dithiopentanylene) (PDTP), a polymer containingPoly(ethene-1,1,2,2-tetrathiol) (PETT) as a main-chain thioetherpolymers, a side-chain thioether polymer having a main-chain consistingof conjugating aromatic moieties, and having a thioether side chain as apendant, Poly(2-phenyl-1,3-dithiolane) (PPDT),Poly(1,4-di(1,3-dithiolan-2-yl)benzene) (PDDTB),poly(tetrahydrobenzodithiophene) (PTHBDT),poly[1,2,4,5-tetrakis(propylthio)benzene] (PTKPTB, orpoly[3,4(ethylenedithio)thiophene] (PEDTT).
 35. The alkali metal cell ofclaim 26, wherein said organic material contains a phthalocyaninecompound selected from copper phthalocyanine, zinc phthalocyanine, tinphthalocyanine, iron phthalocyanine, lead phthalocyanine, nickelphthalocyanine, vanadyl phthalocyanine, fluorochromium phthalocyanine,magnesium phthalocyanine, manganous phthalocyanine, dilithiumphthalocyanine, aluminum phthalocyanine chloride, cadmiumphthalocyanine, chlorogallium phthalocyanine, cobalt phthalocyanine,silver phthalocyanine, a metal-free phthalocyanine, a chemicalderivative thereof, or a combination thereof.
 36. The alkali metal cellof claim 26, wherein said lithium intercalation compound orlithium-absorbing compound is selected from a metal carbide, metalnitride, metal boride, metal dichalcogenide, or a combination thereof.37. The alkali metal cell of claim 26, wherein said lithiumintercalation compound or lithium-absorbing compound is selected from anoxide, dichalcogenide, trichalcogenide, sulfide, selenide, or tellurideof niobium, zirconium, molybdenum, hafnium, tantalum, tungsten,titanium, vanadium, chromium, cobalt, manganese, iron, or nickel in ananowire, nano-disc, nano-ribbon, or nano platelet form.
 38. The alkalimetal cell of claim 26, wherein said lithium intercalation compound orlithium-absorbing compound is selected from nano discs, nano platelets,nano-coating, or nano sheets of an inorganic material selected from: (a)bismuth selenide or bismuth telluride, (b) transition metaldichalcogenide or trichalcogenide, (c) sulfide, selenide, or tellurideof niobium, zirconium, molybdenum, hafnium, tantalum, tungsten,titanium, cobalt, manganese, iron, nickel, or a transition metal; (d)boron nitride, or (e) a combination thereof; wherein said discs,platelets, or sheets have a thickness less than 100 nm.
 39. The alkalimetal cell of claim 1, wherein said alkali metal cell is a sodium metalcell or sodium-ion cell and said cathode active material contains asodium intercalation compound or sodium-absorbing compound selected froman inorganic material, an organic or polymeric material, a metaloxide/phosphate/sulfide, or a combination thereof.
 40. The alkali metalcell of claim 39, wherein said metal oxide/phosphate/sulfide is selectedfrom a sodium cobalt oxide, sodium nickel oxide, sodium manganese oxide,sodium vanadium oxide, sodium-mixed metal oxide,sodium/potassium-transition metal oxide, sodium iron phosphate,sodium/potassium iron phosphate, sodium manganese phosphate,sodium/potassium manganese phosphate, sodium vanadium phosphate,sodium/potassium vanadium phosphate, sodium mixed metal phosphate,transition metal sulfide, or a combination thereof.
 41. The alkali metalcell of claim 39, wherein said inorganic material is selected fromsulfur, sulfur compound, lithium polysulfide, transition metaldichalcogenide, a transition metal trichalcogenide, or a combinationthereof.
 42. The alkali metal cell of claim 39, wherein said inorganicmaterial is selected from TiS₂, TaS₂, MoS₂, NbSe₃, MnO₂, CoO₂, an ironoxide, a vanadium oxide, or a combination thereof.
 43. The alkali metalcell of claim 39, wherein said cathode active material contains a sodiumintercalation compound selected from NaFePO₄, Na_((1-x))K_(x)PO₄,Na_(0.7)FePO₄, Na_(1.5)VOPO₄F_(0.5), Na₃V₂(PO₄)₃, Na₃V₂(PO₄)₂F₃,Na₂FePO₄F, NaFeF₃, NaVPO₄F, Na₃V₂(PO₄)₂F₃, Na_(1.5)VOPO₄F_(0.5),Na₃V₂(PO₄)₃, NaV₆O₁₅, Na_(x)VO₂, Na_(0.33)V₂O₅, Na_(x)CoO₂,Na_(2/3)[Ni_(1/3)Mn_(2/3)]O₂, Na_(x)(Fe_(1/2)Mn_(1/2))O₂, Na_(x)MnO₂,λ-MnO₂, Na_(x)K_((1-x))MnO₂, Na_(0.44)MnO₂, Na_(0.44)MnO₂/C, Na₄Mn₉O₁₈,NaFe₂Mn(PO₄)₃, Na₂Ti₃O₇, Ni_(1/3)Mn_(1/3)Co_(1/3)O₂,Cu_(0.56)Ni_(0.44)HCF, NiHCF, Na_(x)MnO₂, NaCrO₂, Na₃Ti₂(PO₄)₃, NiCo₂O₄,Ni₃S₂/FeS₂, Sb₂O₄, Na₄Fe(CN)₆/C, NaV_(1-x)Cr_(x)PO₄F, Se_(z)S_(y)(y/z=0.01 to 100), Se, Alluaudites, or a combination thereof, wherein xis from 0.1 to 1.0.
 44. The alkali metal cell of claim 1, wherein saidcathode active material constitutes an electrode active material massloading greater than 15 mg/cm².
 45. The alkali metal cell of claim 2,wherein said anode active material constitutes an electrode activematerial mass loading greater than 20 mg/cm².
 46. The alkali metal cellof claim 1, wherein said cathode active material constitutes anelectrode active material mass loading greater than 30 mg/cm².